(4x*4y-y-x-2x*2y)*a=?

(2x+y)(2x-3y)+x(2y+y) 2a(x-y)-4b(x-y) x^2-y^2/x+y-4x(x-y)+y^2/2x-y, {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 已知4x=9y求(1)x+y/y (2)y-x/2x x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 (x+y)(x+2y)(x+3y)(x+4y)=-40 已知集合A={（x,y)| (y-3)/ (x-1)=2,x,y∈R},B={（x,y)| 4x+ay=16,x,y∈ 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y