x+y,x+5y,x-y,5x-y在以上四个式子中任选二个,它们的积是 x^2-(by)^2 形式的概率是多少?（b是一个整数）thx.答案是1/6

{(x,y) |x|+|y| x>y?x:y （x+y-5)*（x+y-5)+（x-y+3)=0 x*x-y*y 已知:3x-5y=0,求x/y,x-y/y,x-y/x 计算：5x/x-y+ 5y/y-x 5x/x-y+5y/y-x (5)a(x+y)-b(x+y)-x-y因式分解 5x(x-y)+2y(x-y) 化简:5(x-y)+2(x+y)-3(x-y) x+y=5; x^y+y^x=17 (y-x)(x-y)^3(y-x)^5怎么算 x-y+5y-4y 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 若(X×X+Y×Y)(X×X+Y×Y-5)=36,则X×X+Y×Y＝ 4x+2y-5x-y (x+5y)(x-7y-1) -X²y+ 5X²y (2x-3y)-(5x-y)