Question 714726
Given:
(1) {{{x^3 + 3x^2 + 5x + 15}}}
Now factor {{{x^2}}} out of the first two terms and 5 out of the third and fourth terms to get
(2) {{{x^2*(x+3) + 5(x+3)}}}
Now factor (x+3) out of (2) and get
(3) {{{(x+3)*(x^2+5)}}}
Set (3) equal to zero gives us the three roots
(4) x = (-3,+i{{{sqrt(5)}}},-i{{{sqrt(5)}}})