Question

先化简再求值：（x²-4x+4分之x-1 -x²-2x分之x+2）÷（x分之4 -1）其中x=-1

Answer 1

原式=[(x-1)/(x-2)^2-(x+2)/x(x-2)]/(4/x-1)

=[(x^2-x-x^2+4)/x(x-2)^2]/[(4-x)/x]

=(4-x)/x(x-2)^2*x/(4-x)

=1/(x-2)^2

=1/(-1-2)^2

=1/9