factor x^3+5x^2-3x-15=0

Question

I cannot remember how to factor to the cubic term 

Answer 1

Hi Shyanna;

x^3+5x^2-3x-15=0

For the FOIL...

FIRST must be (x²)(x)=x³

OUTER must be (x²)(5)=5x²

INNER must be (-3)(x)=-3x

LAST must be (-3)(5)=-15

(x²-3)(x+5)=0

Either parenthetical equation must equal zero...

x²-3=0

x²=3

x=√3

x+5=0

x=-5

 

Answer 2

Factor the LHS of the equation by grouping!