已知x+y=9,x-y=6,求x²-y²-2x-2y的值

已知x,y的值满足方程组x+2y=3,x-y=-2,求x/(x-y)²+x²-y²/(x+ 已知x² +y²+5/4=2x+y,求y-x的值 (1)已知x+y=6,x²-y²=5,求x-y的值（2）若x+y=3,x²+y² 已知y-2x=0,求3x²-2y²/(x+y)(x-y)的值 已知x+3y=2,求代数式(x²-y²/x+y)-【2(x+y)】的值 已知方程组{2x+y=6 x+2y=9},求x+y与x-y的值 已知x+3y=0,求x³+3x²y-2x-6y的值. 已知x²+y²-2xy-6x+6y+9=0,求x+y的值 已知2/x+2/y=根号24,求 x/y(x-y) - y/x(x-y)的值 已知2/x 2/y=根号24,求 x/y(x-y) - y/x(x-y)的值 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 已知x²+y-2xy-6x+6y+9=0,求x-y的值