先化简,再求值;3(x눀+1⼀3y)-2(3⼀2x눀-xy)+(-y+3x),其中x=-2,y=1⼀2

2025-05-19 06:06:16
推荐回答(1个)
回答1:

3(x²+1/3y)-2(3/2x²-xy)+(-y+3x),
=3x²+y-3x²+2xy-y+3x
=2xy+3x
当x=-2,y=1/2时
原式=2×(-2)×1/2+3×(-2)=-2-6=-8