Find all integer roots of f(x). Identify any double roots.
f(x) = 2x4 + 11x3 + 13x2 - 11x - 15
11x(x^2-1) +(x^2-1)(2x^2+15)
(x^2-1)(2x^2+11x+15)
x=1
x=-1
then solve
2x^2+11x+15 =0
(2x+5)(x+3) = 0
x =-5/2
x = -3
f(x) = 2x4 + 11x3 + 13x2 - 11x - 15
(x^2-1)(2x^2+11x+15)
x=1
x=-1
then solve
2x^2+11x+15 =0
(2x+5)(x+3) = 0
x =-5/2
x = -3