Question

Given the polynomial 2x^3+18x^2-18x-162, what is the value of the constant "k" in the factored form?

2x^3+18x^2-18x-162= 2(x+k)(x-k)(x+9)

Answer 1

2x³+18x²-18x-162 =
2(x³+9x²-9x-81)=
2(x²(x+9)-9(x+9))=
2(x²-9)(x+9)=
2(x+3)(x-3)(x+9)

Answer: k=3