解計算
(1)原式=(x²-9)/(x²+2x) × (x²-4)/(x²-3x)
=(x+3)(x-3)/[x(x+2)] × (x+2)(x-2)/[x(x-3)] 約分
=(x+3)/x × (x-2)/x
=(x+3)(x-2)/x²
(2)原式=(x²-y²)/x ÷ (x²+2xy+y²)/x²
=(x+y)(x-y)/x × x²/(x+y)² 約分
=(x-y) × x/(x+y)
=x(x-y)/(x+y)
解方程：1/(x-1)=1/(x²-1)
方程兩邊同時乘最簡公分母(x²-1)
x+1=1
x=0
檢驗(yàn)：把x=0代入最簡公分母
x²-1=0-1=-1≠0
x=0是原方程的根