因式分解和化简求值。(2)

Question

如题所述

Answer 1

9.原式=x^3/(x^2-1)*(x^2-1)/(2x^2-2+x+1-x+1)=x.
10.3/[x(x+2)]=1/[x(x-2)],
去分母得3(x-2)=x+2,
3x-6=x+2,
2x=8,
x=4.
检验：略
11.原式=[1-1/(a+2)]*(a+2)^2/[a(a+1)]
=(a+1)/(a+2)*(a+2)^2/[a(a+1)]
=(a+2)/a,
a=√2时原式=1+√2.
12.原式=2/（x+2)-1/(x-1)*(x-1)^2/(x+2)
=[2-(x-1)]/(x+2)
=(3-x)/(x+2).