b3:...............A) B)

Đáp án:

Giải thích các bước giải:

 `Q=\frac{x^2+2x-8}{x^2+x-12}`

`Q=\frac{x^2-2x+4x-8}{x^2+4x-3x-12}`

`Q=\frac{x(x-2)+4(x-2)}{x(x+4)-3(x+4)}`

`Q=\frac{(x-2)(x+4)}{(x+4)(x-3)}`

`Q=\frac{x-2}{x-3}`

b) `R=\frac{3x^2+5xy-2y^2}{3x^2-7xy+2y^2}`

`R=\frac{3x^2+6xy-xy-2y^2}{3x^2-6xy-xy+2y^2}`

`R=\frac{(3x-y)(x+2y)}{(3x-y)(x-2y)}`

`R=\frac{x+2y}{x-2y}`