1.分子為零 →x=-2 或 x=-3
分母不為零 →x≠±2
故x=-3
2.∵x/2=y/3=z/1/2 ∴x/2=y/3=2z ∴x=4z y=6z
帶入待求式
得：原式=(4z+18z-z) / (8z-6z+z)=21/3=7
3.先求 (a^4+a^2+1) / a^2,再求倒數(shù)
∵a+1/a=3,兩邊平方
∴a2+2+1/a2=9 ∴a2+1/a2=7
(a^4+a^2+1) / a^2=a2+1+1/a2=7+1=8
故a^2/(a^4+a^2+1)=1/8
4.因式分解 x^3-x^2=x2(x-1)
x^2+x-2=x2+2x-x-2=x(x+2)-(x+2)=(x-1)(x+2)
∴原式=[x2(x-1)] / [(x-1)(x+2)] =x2/(x+2)
5.∵1/x-1/y=2 方程兩邊同時(shí)乘以xy
∴y-x=2xy
∴原式=[5xy-3(y-x)] / [-xy-(y-x)] = (5xy-6xy) / (-xy-2xy) =1/3