Question

先化简后求值 【2x-3分之2y-(x-y)】的平方-3分子2xy ， 其中x=1 y=9

Answer 1

[2x-2y/3-(x-y)]*[2x-2y/3-(x-y)]-2xy/3
=(2x-x-2y/3+y)*(2x-x-2y/3+y)-2xy/3
=(x+y/3)*(x+y/3)-2xy/3
=x*x+2xy/3+y*y/9-2xy/3
=x*x+y*y/9
代入x=1y=9
得到=1*1+9*9/9
=1+9=10

Answer 2

解：[2x-2y/3-(x-y)]^2-2xy/3
=(2x-x-2y/3+y)^2-2xy/3
=(x+y/3)^2-2xy/3
=x^2+2xy/3+y^2/9-2xy/3
=x^2+y^2/9
代入x=1y=9
得到=1*1+9*9/9
=1+9=10