Solve the equation by factoring

Question

(x-9)(x2 + 9x + 18)=0

How do i solve this step by step?

Answer 1

To factor x² + 9x + 18, find 2 numbers a and b such that

 

ab = 18

a + b = 9

 

Note that 3 and 6 are such numbers.  Then

 

x² + 9x + 18 = (x + 3)(x + 6)

 

(x - 9)(x² + 9x + 18) = (x - 9)(x + 3)(x + 6) = 0

 

x = 9, -3, -6

 

 

Answer 2

(x-9)(x^2+9x+18) = 0
factor one step further:
(x-9)(x+3)(x+6)=0
now set each factor equal to zero and solve for x. we want to find the x values at which your function = 0:
x-9=0 --> x=9
x+3=0 --> x=-3
x+6=0 -->x=-6

 

and you're done!