Why is it that 9x^2+36 becomes 9(x^2 - 4y^2)?

[Max CR]

Why is it that 9x^2+36 becomes 9(x^2 - 4y^2)?

Why doesnt it get factored similiar to the example below.

6c^2 - 600 becomes 6(c+10)(c-10)

 

[galactus]

It doesn't. There is a problem somewhere.

 

[Xelthen]

I think he means 9x² + 36y²
It's because you factor out the 9 so it becomes 9(x² + 4y²), but x² + 4y² can't be factored.

 

[Denis]

Moral of da story:
a^2 - b^2 = (a + b)(a - b)
a^2 + b^2 = a^2 + b^2 :roll: