Question

设A=2x²-3xy+y²-x+2y,B=4x²-6xy+2y²+3x-y 若|x-2a|+(y+3)²=0,且B-2A=a,求A的值

Answer 1

由|x-2a|+(y+3)²=0得：x=2a，y=-3，
B-A=(4x²-6xy+2y²+3x-y)-2(2x²-3xy+y²-x+2y)
=5X-5Y
∴10a+15=a
9a=-15
a=-5/3.

追问

那A咧？？我求大A不是小a........

追答

X=-10/3，y=-3
A=2x²-3xy+y²-x+2y
=2(-10/3)^2-3(-10/3)*(-3)+(-3)^2-(-10/3)+2(-3)
=200/9-30+9+10/3-6
=230/9-27
=-13/9

Answer 2

wzhq777 回答错了，正确答案是-13/9,啊哦，看错了，对不起啦