已知(x+y)²=9,(x-y)²=1,求值:①x²+y² ②xy ③x^4+y
已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y²
已知x+y=1,xy=-二分之一,求x(x+y)(x-y)-x(x+y)²
已知x²+y²-8x+6y+25=0,求(x-y+4xy/x-y)(x+y-4xy/x+y)
若x+y=9,xy=16,求值.(1)x²+y² ( 2)x²+y²-4xy
已知非零有理数x,y满足x²-4xy+4y²=0,求x-y/x+y-y-x/x+y的值.
x²+xy/(x-4y)(x+y),其中x=4,y=-1
先化简,在求值9x³-xy²/(3x+y)(9x²-6xy+y²)其中x=1,y
已知x-5y=0,化简(2x+y)(x-y)/x²+2xy+y²并求值.
先化简,再求值:3x²—[2x²y—(xy—x²)]+4x²y,其中x=—1,y
已知X²+Y²+X²Y²-4XY+1=0 求:(X-Y)^2008-(XY)^2
已知实数x,y满足x²+y²-xy+2x-y+1=0 求x y
已知x+y,且x²-2x=7,y²-2y=7求①x+y②2x+xy+y²