先化简再求值(X+1分子1-1-X分子1)÷X²-1分之1其中X等于2分之1
问题描述：
先化简再求值(X+1分子1-1-X分子1)÷X²-1分之1其中X等于2分之1
答
答：
(X+1分子1-1-X分子1)÷X²-1分之1其中X等于2分之1
=[ 1/(x+1)-1/(1-x)]÷[1/(x^2-1)]
={ (x-1)/[(x+1)(x-1)] +(x+1)/[(x-1)(x+1)] } ×(x^2-1)
=[(x-1)+(x+1)]÷(x^2-1)×(x^2-1)
=2x
=2×(1/2)
=1
答
[1/(X+1)-1/(1-X)]÷1/(X²-1)
=[1/(X+1)-1/(1-X)]x(X²-1)
=1/(X+1)x(X²-1)- 1/(1-X)x(X²-1)
=1/(X+1)x(X²-1)+ 1/(X-1)x(X²-1)
=(X-1)+(X+1)
=X-1+X+1
=2X
=2*1/2
=1