Jika Polinom 2x^4-3x^3+ax^2+5x+b dibagi dengan x^2-x-6 bersisa 6x+5, maka nilai a-b sama dengan..?

Faktor. x²-x-6 = 0
(x-3)(x+2) = 0
x = 3, x = -2

f(3) = 2(3)^4-3(3)³+a(3)²+5(3)+b
s(3) = 6(3)+5
= 23

f(3) = s(3)
162-81+9a+15+b = 23
9a+b = -73

f(-2) = 2(-2)^4-3(-2)³+a(-2)²+5(-2)+b
s(-2) = 6(-2)+5
= -7

f(-2) = s(-2)
32+24+4a-10+b = -7
4a+b = -53

9a+b = -73
4a+b = -53
_________-
5a. = -20
a = -4
b = -37

a-b = -4+37
= 33