Question

设A=2x^2-3xy+y^2-x+2y,B=4x^2-6xy+2y^2+3x-y.若/x-2a/+(y+3)^2=0，且B-2A=a，求A的值

写的详细一点，对了，答案上写的最终A应该等于283，谢谢您的帮助，我非常需要，希望您可以快一点！！！

Answer 1

|x-2a|+(y+3)^2=0
x=2a，y=-3

B-2A=a
a=4x^2-6xy+2y^2-3x-y-2(2x^2-3xy+y^2-x+2y)

=4x^2-6xy+2y^2-3x-y-4x^2+6xy-2y^2+2x-4y
=-x-5y

|x-2a|
=|x-2(-x-5y)|

=|x+2x+10y|
=|3x+10y|
=|3x-30|
=0
解得x=10

A=2x^2-3xy+y^2-x+2y
=(x-y)(2x-y)-x+2y
=13×23-10-6
=283