tolong kerjakan pakai cara kerja.

4) C. f(x) = x^2 - 2x - 3
Pembuktian :
x=1 ~ (1)^2 - 2(1) - 3 = 1-2-3 = -4
x=4 ~ (4)^2 - 2(4) -3 = 16-8-3 = 5

5) 2x^2 + 3x - 6 = 0
a=2 b=3 c =(-6)
x1+x2 = -b/a = -3/2
x1.x2 = c/a = -6/2 = -3
~2x1(x2)^2 + 2(x1)^2 x2
= 2x1x2 ( x2+x1)
= 2(-3) (-3/2)
= -6 (-3/2)
= 9