a的平方(x-y)+16(y-x)；解方程组{2x+y=3,x-1/2y=2

1、=a²(x-y)-16(x-y)
=(x-y)(a²-16)
=(x-y)(a+4)(a-4)
2由(2)得
x=2+y/2 (3)
把(3)代入(1)得
4+y+y=3
∴y=-1/2
把y=-1/2代入(3)得
x=2-1/4=7/4
∴x=7/4
y=-1/2