Question

Jika x1 dan x2 adalah akar akar dari x2 + (2k+1)x+(4k+2) = 0 dan x1 =2 maka x1x2 =

Answer 1

X1 = 2 --> x^2 + (2k+1)x + (4k+2) = 0
2^2 + (2k+1)(2) + (4k+2) = 0
4 + 4k + 2 + 4k + 2 = 0
8k + 8 = 0
8k = -8
k = -8 : 8
k = -1

x^2 + (2 × (-1) + 1)x + (4 × (-1) + 2) = 0
x^2 + (-2 + 1)x + (-4 + 2) = 0
x^2 - x - 2 = 0
a = 1
b = -1
c = -2

x1x2 = c/a
x1x2 = -2/1
x1x2 = -2

Answer 2

Dari soal

x1 + x2 = -2k -1

2 + x2 = -2k -1

x2 = -2k -3


x1.x2 = 4k+2

2(-2k-3) = 4k + 2

-4k -6 = 4k +2

-8k = 8

k = -1

Sehingga x1.x2 = 2(2-3) = 2.(-1) = -2