初二的数学题~~~急,速度~~~积分高
1.已知ab=1,求1/(a²-1)+1/(b²-1)的值
2.已知1/x+1/y=-1/(x+y),求y/x+x/y的值
3.已知(x+3)/(x+2)=1/(√3+√2+1),求(x-3)/(2x-4)÷[5/(x-2)-x-2]的值