1.解方程组.(x+2)平方-(y-3)平方=(x+y)(x-y),
问题描述:
1.解方程组.(x+2)平方-(y-3)平方=(x+y)(x-y),
x-3y=2
2.化简求值.
(1) 已知(x-y)平方=625/36,x+y=7/6,求xy+4的值
(2)已知a-b=2,b-c=-3,c-d=5,求代数式(a-c)(b-d)/(a-d)
答
1.(x+2)^2-(y-3)^2=(x+y)(x-y)...(1)x-3y=2...(2)由(2)得x=3y+2...(3),将(3)代入(1)得:(3y+4)^2-(y-3)^2=(4y+2)(2y+2),解得:y=-1/6...(4),代入(2)得:x=3/22.1(X-Y)^2=X^2+2XY+Y^2-4XY=(X+Y)^2-4XY=49/36-4...