Câu 1. (1,5 điểm) Rút gọn: a) $(x+3)^2+(3 x-2)(x+4)$ b) $5 x y(2 x+3 y)$ c) $\frac{3}{x-1}+\frac{1}{x+1}+\frac{x+3}{x^2-1}$

`@` 090125

Đáp án:

a) `(x+3)^2+(3x-2)(x+4)`

`= x^2+6x+9+3x^2+12x-2x-8`

`= 4x^2+16x+1`

b) `5xy(2x+3y)`

`= 5xy*2x+5xy*3y`

`= 10x^2y+15xy^2`

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

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

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

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

`= (5x+5)/((x-1)(x+1))`

`= (5(x+1))/((x-1)(x+1))`

`= 5/(x-1)`