There are four different methods that can be used to solve a quadratic equation. Which are:

1. Factorization;
2. Completing the square;
3. The general quadratic formula;
4. Graphical solution.
Each of the four methods above can be used to solve specific types of quadratic equation, however our main focus shall be to apply the general quadratic formula also known as the “Almighty formula”.
As the alias implies, it can be used to solve any standard quadratic equation. This formula works where all else have failed.
For a standard quadratic equation of the form: ax² + bx + c = 0;

EXAMPLE: Solve 4x²-11x - 21 = 0

See more examples here:
http://9jababa.com/how-to-solve-any-quadratic-equation-using-the-almighty-formula

In addition...

There is a particular textbook I use for this topic back then. I used to have difficulty at it until I found this textbook. Since I begin using the textbook, it's become very very simple and a favorite topic.

They're majorly three textbooks. You can also download them in pdfs into your phone.

The first one is
Hidden Facts Further Mathematics

The second one is
Comprehensive Mathematics

The third one is
Project (1-3)Further Mathematics

Bonus & Necessary for starters
New General Mathematics Textbook (1-3)

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Hidden Facts is 2500N instead of 5000N in hardcopy..
Comprehensive Mathematics is 1500N instead of 2500N in hardcopy.
Project Further Mathematics 1-3 & New General Mathematics 1 -3 is 3000N each (Three textbooks combined) Instead of 6000N each in hardcopy.

Here is the link to download the books in PDFs without stress!

https://www.books.barrkolawole.com/?s=mathematics&post_type=product

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