Question

Hasil kali dua bilangan asli tang berselisih 4 adalah 192.jika x1>x2 .maka nilai 2x1 + 3x2 adalah...
a.64 b.68 c.72 d.78

Answer 1

(x1 - x2)^2 = x1^2 + x2^2 - 2x1x2
4^2 = x1^2 + x2^2 - 2.192
16 = x1^2 + x2^2 - 384
x1^2 + x2^2 = 400

(x1 + x2)^2 = x1^2 + x2^2 + 2x1x2
(x1 + x2)^2 = 400 + 2.192
(x1 +x2)^2 = 784
x1 + x2 = √784
x1 + x2 = 28

x1 - x2 = 4
x1 + x2 = 28
___________ +
2x1 = 32
x1 = 16

x1 - x2 = 4
x2 = x1 - 4
x2 = 16 - 4
x2 = 12

2x1 + 3x2 = 2.16 + 3.12
= 68