△若x^2+2xy+y^2-a(x+y)+25是完全平方式若x^2+2xy+y^2-a(x+y)+25是完全平方式,求a的值.以前的东西都忘了,给讲讲啊~

若(x+y)(x-y)^2-xy(x+y)=A(x+y),则A=什么 (-x-y)(x^2+xy+y^2) 化简x^-y^/x^-2xy+y^ 2*(x-y)²(y-x)(xy) （x^2+xy/x-y)/（xy/x-y)计算 若x^2+xy+y=14,y^2+xy+x=28,求x+y X-Y/2X+2Y XY/X+Y² 因式分解：x×x-xy-2y×y-x-y 若1/x-1/y=2,求3x-2xy-3y/x-xy-y的值3x-2xy-3y/x-xy-y 不好意思，是3x-2xy-3y/x-2xy-y 因式分解（x+y-2xy)(x+y-2)+(xy-1)^2设x+y=a,xy=b, 因式分解:12xy^2(y-x)+xy^3(x-y)+4x^2y(x-y) (x-y)[(x+y)^2-xy]+(x-y)[(x-y)^2+xy] .(x+y-2)(x+y-2xy)+(xy-1)^2 (x^2-xy)y÷y-x/xy怎么做? 代数 x^-y^/ x^-(y-z)^ 除以 x^+2xy+y^/(x-y)^-z^ 乘 x^+xy-xz/x^-xy (x+y)/x /(x-(2xy-y^2)/x) 因式分解 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 x^2-xy/xy-y^2约分