x-2y=-1 ①
3(x-2)=1-y ②
由①,得x=2y-1 ③
将③代入②中,得
3(2y-3)=1-y
6y-9=1-y
7y=10
y=10/7
将y=10/7代入③中,得
x=20/7-1=13/7
4x-3y=-2 ①
x/4+y/6=3 ②
即3x+2y=36 ③
①×2,②×3,得
8x-6y=-4 ④
9x+6y=108 ⑤
④+⑤,得
17x=104
x=104/17
将x=104/17代入③中,得
y=150/17
(x-1)(x-2)-3x(x+3)-(x-1)^2
=x^2-3x+2-3x^2-9x-(x^2-2x+1)
=x^2-3x+2-3x^2-9x-x^2+2x-1
=-3x^2-10x+1
=-3×9-10×3+1
=-27-30+1
=-56
(-1/2)^2/(-2)^3×(-2)^2
=(1/4)/(-8)×4
=-1/32×4
=-1/8