Question

先化简,再求值：(1-x+2分之1)除以x的平方-4分之x的平方+2x+1,其中x=-3

Answer 1

1/(1-x+2)/(x^2+2x+1)/(x^2-4),其中x=-3

=1/(3-x)*(x+2)(x-2)/(x+1)^2

=(x+2)(x-2)/(x+1)^2(3-x)

=5/24