## allea_marie 2 years ago How do you solve 5x² - 20x² (GCF)

1. AravindG

GCF means?

2. AravindG

-15x^2

3. CheetahBooks1

GCF means Greatest Common Factor.

4. CheetahBooks1

Am I right?

5. AravindG

6. CheetahBooks1

Hello?

7. scarydoor

There needs to be more here, for there to be something to solve.

8. allea_marie

Yes it stands for Greatest Common Factor

9. scarydoor

so what are the two numbers that you want to find the greatest common factor of?

10. CheetahBooks1

But why do you need GCF to solve this? It is quite simple. Just subtract 5-20 and carry over the x^2. That would be -15x^2

11. allea_marie

Okay thanks, how would you solve 2x² - 21x=54

12. scarydoor

that one can be solved by factorising the polynomial.

13. scarydoor

\[ 2x^2 - 21x =54 \] \[2x^2 - 21x - 54 = 0 \] Now you want to solve: \[(2x + a)(x +b) = 2x^2 - 21x - 54 \] Note that you must have \[ a*b = -54 \]

14. scarydoor

this won't always work so easily. But I can see here that it does.

15. allea_marie

Okay thank you