factor completely. k^4 - 9k^2 + 2K^3 - 18k - 15k^2 + 135

Question

factor the expression completely

Answer 1

(k^4-9k^2)+(2k^3-18k)-(15k-135)=

k^2(k^2-9)+2k(k^2-9)-15(k^2-9)=

(k^2-9)(k^2+2k-15)=

(k+3)(k-3)(k+5)(k-3)