tolong dibantu yaaaaaa

jawab

A = B^t
A = C
B^t = C

x + y = 1
x  - y =  3 || (+)
2x = 4
x = 2

x + y = 1
2 + y = 1
y = - 1

nilai (x) - 2(x)(y) + (y) =
= (2) - 2(2)(-1) +(-1)
= 2 + 4 - 1
= 5