Question

1.求代数式的值：x²-2x/x²-4 ÷ （x-2 - 2x-4/x+2）,其中x=3.

Answer 1

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

=x/(x+2)÷(x²-4-2x+4)/(x+2)

=x/(x+2)÷(x²-2x)/(x+2)

=x/(x+2)*(x+2)/x(x-2)

=1/(x-2)

=1/(3-2)

=1