Question

先化简,再求值:当x=时,代数式4×2+2-1-2(1-x+x)的值()

先化简,再求值(x/x^2-1)×(x^2+x/x^2),其中x=2
先将代数式(x^2+x)×(1/x+1)化简,再从-1,1两数中选取一个适当的数作为x的值带入求值

Answer 1

(1)(x/x^2-1)*(x^2+x)/x^2)
=[x/(x+1)(x-1)]*[x(x+1)/x^2]
=1/(x-1)
代入x=2 原式=1/(2-1)=1
(2)(x^2+x)*(1/x+1)
=x(x+1)/(x+1)
=x
当x=1时,原式=1