Tolong caranya ya....

f(x) : (x + 5) bersisa (2x - 1)
x = -5 => sisa = 2(-5) - 1 = -11
f(-5) = -11

f(x) : (x - 3) bersisa 7
f(3) = 7

f(x) : (x^2 + 2x - 15) bersisa ..... ?
Misal sisanya : (ax + b)

f(-5) = -5a + b = -11
f(3) = 3a + b = 7
--------------------------- -
......... -8a = -18 => a = 18/8 = 9/4

3a + b = 7
3(9/4) + b = 7
b = 7 - 27/4 = 1/4

Sisa = ax + b = 9/4 x + 1/4