I know you must be a lover of maths! Thanks for viewing...
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I don't know where I'm getting this wrong. Please correct me if it's wrong:
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Quest.: Solve the following:
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12m + 12n = -7 ............ (i)
4m - 3n = 7 ............ (ii)
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What I did:
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Multiply (i) by 1 and (ii) by 4
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12m + 12n = -7 ........... (iii)
16m - 12n = 28 (iv)
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Add (iii) and (iv) to eliminate n
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28m = 21 ............ (v)
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Divide both sides of (v) to isolate m
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m = 21/28
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I stopped there. But when I checked the answer on the book, it was reading a different thing. Please, where am I getting it wrong? I am open to learning.

Work backwards from the answer.....

By the power vested in me I declare you right

12m + 12n = -7 .....I
4m - 3n = 7.....ii
u attempted employing elimination method, bt u missed at this point. just continue from here.
(4)X (12m + 12n = - 7 )
(12)X (4m - 3n = 7 )

Laive:
I know you must be a lover of maths! Thanks for viewing...
.
I don't know where I'm getting this wrong. Please correct me if it's wrong:
.
Quest.: Solve the following:
.
12m + 12n = -7 ............ (i)
4m - 3n = 7 ............ (ii)
.
What I did:
.
Multiply (i) by 1 and (ii) by 4
.
12m + 12n = -7 ........... (iii)
16m - 12n = 28 (iv)
.
Add (iii) and (iv) to eliminate n
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28m = 21 ............ (v)
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Divide both sides of (v) to isolate m
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m = 21/28
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I stopped there. But when I checked the answer on the book, it was reading a different thing. Please, where am I getting it wrong? I am open to learning.

You multiplied wrongly, it should be
12m+12n=-7
4m-3n=7
multiply eqn 1 by 3 and eqn 2 by 12
36m+36n=-21
48m-36n=84...I guess you can carry on from there m should be =1

ruxxz:
12m + 12n = -7 .....I
4m - 3n = 7.....ii
u attempted employing elimination method, bt u missed at this point. just continue from here.
(4)X (12m + 12n = - 7 )
(12)X (4m - 3n = 7 )

48m + 48n = -28 ........ (i)
48m - 36n = 84 ........ (ii)
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Subtracting:
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84n = - 112
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Isolating n:
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n = - 112/84
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n = - 7/6
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Is that what you mean? If yes, it's different from what is in the book here.

hardbody:
Work backwards from the answer.....

Make it clear, please...

Donovela:
You multiplied wrongly, it should be
12m+12n=-7
4m-3n=7
multiply eqn 1 by 3 and eqn 2 by 12
36m+36n=-21
48m-36n=84...I guess you can carry on from there m should be =1

Yeah, but the answer in the book here is fractional. Try using the substitution method as well, your assumed answer might be different.

Mr laive.
I solved it and this was my answers.


m=3/4
N=-4/3

check the text book. . .
if I'm right I will solve it here. but if wrong someone should help us out.




*****modified*****
since you said it's correct lemme show ya'll how I solved it. . . .


12m + 12n = -7. (×1)
4m - 3n = 7. (×3)
__________________________
12m + 12n = -7
-
12m + 9n = 21
__________________________
12n + 9n = -7-21
__________________________
21n = -28

therefore N = -28/21 = -4/3.


now to get M substitute N=-4/3 in any of the first equation. let's take

4m - 3n = 7
4m - 3(-4/3) = 7
_________________________

4m +12/3 = 7

_________________________

4m + 4 = 7

_________________________

4m = 7 - 4

4m = 3

therefore M = 3/4.

laive see am o.

ERUDITEE:
Mr laive. I solved it and this was my answers.

m=3/4 N=-4/3
check the text book. . . if I'm right I will solve it here. but if wrong someone should help us out.

Exaaaaaaaaaaaactly! Wow! Please, I am hungry to know how you did it. Care to share it??

Laive:

48m + 48n = -28 ........ (i)
48m - 36n = 84 ........ (ii)
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Subtracting:
.
84n = - 112
.
Isolating n:
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n = - 112/84
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n = - 7/6
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Is that what you mean? If yes, it's different from what is in the book here.

subtracting
84n = -112
n = -112/84
= -56/42
= - 8/6
n = - 4/3

ERUDITEE:
Mr laive.
I solved it and this was my answers.


m=3/4
N=-4/3

check the text book. . .
if I'm right I will solve it here. but if wrong someone should help us out.




*****modified*****
since you said it's correct lemme show ya'll how I solved it. . . .


12m + 12n = -7. (×1)
4m - 3n = 7. (×3)
__________________________
12m + 12n = -7
-
12m + 9n = 21
__________________________
12n + 9n = -7-21
__________________________
21n = -28

therefore N = -28/21 = -4/3.


now to get M substitute N=-4/3 in any of the first equation. let's take

4m - 3n = 7
4m - 3(-4/3) = 7
_________________________

4m +12/3 = 7

_________________________

4m + 4 = 7

_________________________

4m = 7 - 4

4m = 3

therefore M = 3/4.

laive see am o.

Thanks a lot! Na dat 21/28 make me lost. It's been long, please remind me. Sounds silly, right? That's how I learn...

ruxxz:
subtracting
84n = -112
n = -112/84
= -56/42
= - 8/6
n = - 4/3

OMG! I wish I can slap myself to your hearing! Thanks a million. But na that 21/28 dey give me small headache. Sounds silly! But help remind me. Primary 2 stuff sha... Na learning time oh.

Laive:

OMG! I wish I can slap myself to your hearing! Thanks a million. But na that 21/28 dey give me small headache. Sounds silly! But help remind me. Primary 2 stuff sha... Na learning time oh.

No qualms boss. Maths cud b funny atimes. Basic operations hav cost us valuable marks severally.

Try guassian elimination method

jessetom:
Try guassian elimination method

Care to share?? Ready to learn...

Thank you all for your wonderful contributions, especially Chiefolododo, Ruxxz, Eruditee and the rest who "Liked" & "Shared".
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I just remembered yesterday that to simplify 21/28, I would have just looked for a HCF which is 7.
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21/7 = 3 and
28/7 = 4
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=> m = 3/4
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Thank you once again... I guess we can always solve subsequent maths problems together.

Laive:

Care to share?? Ready to learn...

It's a simple matrix method.

You just have to reduce the augmented matrix to Echelon form by elementary row transformations. It's really fun. You can use it for higher order systems of linear equations.

But if you mind, try crammer rule

Laive:
Thank you all for your wonderful contributions, especially Chiefolododo, Ruxxz, Eruditee and the rest who "Liked" & "Shared".
.
I just remembered yesterday that to simplify 21/28, I would have just looked for a HCF which is 7.
.
21/7 = 3 and
28/7 = 4
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=> m = 3/4
.
Thank you once again... I guess we can always solve subsequent maths problems together.

that's good, keep bringing them.
we are all learning.

jessetom:


It's a simple matrix method.

You just have to reduce the augmented matrix to Echelon form by elementary row transformations. It's really fun. You can use it for higher order systems of linear equations.

But if you mind, try crammer rule

Wow! Quite strange to me...

Another one here o!
I don't know where I'm wrong. It's still simultaneous equations:
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Que.1
xy = 21 .......... (i)
x + 5y = 22 ..... (ii)
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Que.2
x/2 - y/5 = 1 ...... (i)
y - x/3 = 8 ......... (ii)
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What I tried:
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Que.1
From (ii), make x the subject
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x = 22 - 5y ...... (iii)
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Substitute (iii) for x in (i)
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=> y(22 - 5y) = 21
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=> 22y - 5y² = 21
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Rearranging the quadratic equation:
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-5y² + 22y -21 = 0
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Factorizing the quadratic equation:
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=> (5y - 7)(-y + 3) = 0
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=> 5y - 7 = 0 or
=> -y + 3 = 0
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Solving both linear equations:
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=> 5y = 7 i.e. y = 7/5
=> -y = 3 i.e. y = 3
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Substitute both values of y in (i) above.
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When y = 7/5
=> xy = 21
=> 7x/5 = 21 or 7x = 105
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Therefore x = 15 and y = 7/5
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When y = 3
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3x = 21 or x = 21/3
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Therefore y = 3 and x = 7
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But the book says I'm wrong!

Laive:
Another one here o!
I don't know where I'm wrong. It's still simultaneous equations:
.
Que.1
xy = 21 .......... (i)
x + 5y = 22 ..... (ii)
.
Que.2
x/2 - y/5 = 1 ...... (i)
y - x/3 = 8 ......... (ii)
.
What I tried:
.
Que.1
From (ii), make x the subject
.
x = 22 - 5y ...... (iii)
.
Substitute (iii) for x in (i)
.
=> y(22 - 5y) = 21
.
=> 22y - 5y² = 21
.
Rearranging the quadratic equation:
.
-5y² + 22y -21 = 0
.
Factorizing the quadratic equation:
.
=> (5y - 7)(-y + 3) = 0
.
=> 5y - 7 = 0 or
=> -y + 3 = 0
.
Solving both linear equations:
.
=> 5y = 7 i.e. y = 7/5
=> -y = 3 i.e. y = 3
.
Substitute both values of y in (i) above.
.
When y = 7/5
=> xy = 21
=> 7x/5 = 21 or 7x = 105
.
Therefore x = 15 and y = 7/5
.
When y = 3
.
3x = 21 or x = 21/3
.
Therefore y = 3 and x = 7
.
But the book says I'm wrong!

Ur answers satisfy the equations(sub x and y into d equations, u'd c dat they'r correct). wonder wots wrong in it.

same here o.

this one e dun tey tey I solve am o.


chiefolododo oya take over.

ruxxz:
Ur answers satisfy the equations(sub x and y into d equations, u'd c dat they'r correct). wonder wots wrong in it.

Although I have not tried using the general formula, but the book says x = 5.2 or -0.8 and y = 2 or 6/5 .
.
How about question 2 above??

We are not all learning , this one is too elementary for me to lrarn

ERUDITEE:



that's good, keep bringing them.
we are all learning.

chiefolododo:
We are not all learning , this one is too elementary for me to lrarn

wow!! thank God it's too elementary for you.

laive we'v got another guru.

oya chiefolododo solve it since you know how to.

Laive:

Although I have not tried using the general formula, but the book says x = 5.2 or -0.8 and y = 2 or 6/5 .
.
How about question 2 above??

question 2.
x/2 - y/5 = 1...i.
y - x/3 = 8.......ii

from i, 5x - 2y = 10 ....iii
from ii, 3y - x = 24.......iv

from iv, x = 3y - 24...v
sub (v) in (iii)
15y - 120 - 2y = 10
13y = 130
y = 10...

sub y in (iv)
3 (10) - x = 24
x = 6...

x = 6, y = 10

chiefolododo:
We are not all learning , this one is too elementary for me to lrarn

Chiefolododo, if you say so o! But what is the easiest way to factorize a quadratic equation without using formula.
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I always find it hard to factor out numbers in a quadratic equation. Please gave me a trick!

Laive:

Wow! Quite strange to me...

Hmm. But you can program this. It's quite simple na. I see you are programmer. Use coding to illuminate the way

The easiest is by using quadratic formular but if you can't use that , then factorize . completing the square method is not an option at all [
quote author=Laive post=48898988]
Chiefolododo, if you say so o! But what is the easiest way to factorize a quadratic equation without using formula.
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I always find it hard to factor out numbers in a quadratic equation. Please gave me a trick![/quote]

ruxxz:
question 2. x/2 - y/5 = 1...i. y - x/3 = 8.......ii
from i, 5x - 2y = 10 ....iii from ii, 3y - x = 24.......iv
from iv, x = 3y - 24...v sub (v) in (iii) 15y - 120 - 2y = 10 13y = 130 y = 10...
sub y in (iv) 3 (10) - x = 24 x = 6...
x = 6, y = 10

Wow! Thanks a lot bro!

chiefolododo:
The easiest is by using quadratic formular but if you can't use that , then factorize . completing the square method is not an option at all [
quote author=Laive post=48898988]
Chiefolododo, if you say so o! But what is the easiest way to factorize a quadratic equation without using formula.
.
I always find it hard to factor out numbers in a quadratic equation. Please gave me a trick!

Okay o! I dey learn o... However, it's not as if I can't use the formula. But some examinars are always specific. The instruction might be to solve without using the formula.