`x/(x+y) + (2xy)/(x^2-y^2) - y(x+y)`

`= (x(x-y))/(x^2-y^2) + (2xy)/(x^2-y^2) - (y(x-y))/(x^2-y^2)`

`= (x^2 - xy + 2xy - xy + y^2)/(x^2-y^2)`

`= (x^2+y^2)/(x^2-y^2)`

`a, x/(x+3) + (2-x)/(x+3) = (x+2-x)/(x+3) = 2/(x+3)`

`b, (x^2y)/(x-y) - (xy^2)/(x-y) = (x^2y-xy^2)/(x-y) = (xy(x-y))/(x-y)= xy`

`c, (2x)/(2x-y) - (y)/(2x-y)`

`= (2x-y)/(2x-y) = 1`

`a, (3x^2y)/(2xy^5)`

`= (3x)/(2y^4)`

`b, (3x^2-3x)/(x-1)`

`= (3x(x-1))/(x-1)`

`= 3x`

`c, (ab^2-a^2b)/(2a^2+a)`

`= (b(a-b))/((2a+1))`

`d, (12(x^4-1))/(18(x^2-1)) = (2(x^2+1))/3`.

`a, ? = (3x+1)(x+1) = 3x^2 + 4x + 1`

`b, ? = (x^2+2x)(x+2) = x^3 +4x^2 + 4x`

`a, (3ac)/(a^3b) = (3c)/(a^2b)`

`(6c)/(2a^2b) = (3c)/(a^2b)`

Vậy hai phân thức `=` nhau

`b, (3ab-3b^2)/(6b^2) = (3b(a-b))/(6b^2) = (a-b)/(2b)`

Vậy hai phân thức `=` nhau

Thiếu `c,`

`a, x ne 6`

`b, x ne -3y`

`c, x in RR`.

`a, A = (3x(x+1))/(x+1)^2 = (3x)/(x+1)`

Thay `x = -4` ta có: `(3.(-4))/(-4+1) = 4`.

`b, B = (b(a-b))/((a-b)(a+b)) = b/(a+b)`

Thay `a = 4; b =-2`

`-2/(4-2) = -1`

`(a^2-b^2)/(a^2b + ab^2) = ((a-b)(a+b))/(ab(a+b)) = (a-b)/(ab)`.

`(a-b)/(ab) = ((a-b)(a+b))/(ab(a+b)) = (a^2-b^2)/(ab(a+b))`

`a, (3x^2+6xy)/(6x^2) = (x+2y)/(3x)`

`b, (2x^2-x^3)/(x^2-4) = (x^2(2-x))/((x-2)(x+2))`

`= -x^2/(x+2)`

`c, (x+1)/(x^3+1) = 1/(x^2-x+1)`