Đáp án:
1)
` (x^2-1)/(x(x-1)) = ((x-1(x+1))/(x(x-1)) = (x+1)/x `
` => C`
2)
` ( x^2 -2x +1) : (x-1) = (x-1)^2 : (x-1)= (x-1)`
` => B`
3)
ĐKXD : ` x^2+ 2x \ne 0 => x(x+2) \ne 0 => x \ne 0 ; x \ne -2`
` => D`
4)
ĐK : ` x^2 - 4 \ge 0 => x^2 \ge 4 => x \ge ± 2`
` => C`
5)
` (x^2- 2xy + y^2)- 1`
` = (x-y)^2 -1`
` = (x-y-1)(x-y+1)`
` => A`
6)
` (x+y)^2 - (x-y)^2`
` = x ^2+ 2xy+ y^2 - x^2 +2xy -y^2`
` = 4xy`
` => C`