Giúp tớ voi ạaa tớ cmonn

Câu 19 : 

`a)` `\frac{x}{y^2}` `+` `\frac{3}{y^2}`

`=` `\frac{x+3}{y^2}`

`b)` `\frac{x+y}{x^2y}` `+` `\frac{y+7}{x^2y}`

`=` `\frac{x+y+y+7}{x^2y}`

`=` `\frac{x+2y+7}{x^2y}`

`c)` `\frac{x+5}{x+2}` `+` `\frac{2x+1}{x+2}`

`=` `\frac{x+5+2x+1}{x+2}`

`=` `\frac{3x+6}{x+2}`

`=` `\frac{3.(x+2)}{x+2}`

`=` `3`

`d)` `\frac{2x-1}{x-1}` `-` `\frac{x-2}{x-1}`

`=` `\frac{2x-1-x+2}{x-1}`

`=` `\frac{x+1}{x-1}`

`e)` `\frac{x+1}{x-2}` `+` `\frac{x-10}{x-2}` `+` `\frac{x+3}{x-2}`

`=` `\frac{x+1+x-10+x+3}{x-2}`

`=` `\frac{3x-6}{x-2}``\frac{3.(x-2)}{x-2}`

`=` `3`

`f)` `\frac{4x+5}{x+2}` `-` `\frac{2x+1}{x+2}`

`=` `\frac{4x+5-2x-1}{x+2}`

`=` `\frac{2x+4}{x+2}`

`=` `\frac{2.(x+2)}{x+2}`

`=` `2`

`g)` `\frac{x^2+4}{y.(x+3)}` `+` `\frac{6x+5}{y.(x+3)}`

`=` `\frac{x^2+4+6x+5}{y.(x+3)}`

`=` `\frac{x^2+6x+9}{y.(x+3)}`

`=` `\frac{(x+3)^2}{y.(x+3)}`

`=` `\frac{x+3}{y}`

`h)` `\frac{5x^2-17}{4xy-10y}` `-` `\frac{x^2+8}{4xy-10y}`

`=` `\frac{5x^2-17-x^2-8}{4xy-10y}`

`=` `\frac{4x^2-25}{4xy-10y}`

`=` `\frac{(2x-5).(2x+5)}{2y.(2x-5)}`

`=` `\frac{2x+5}{2y}`

`i)` `\frac{x^2+2}{2xy-2y}` `-` `\frac{2x+1}{2y.(x-1)}`

`=` `\frac{x^2+2-2x-1}{2y.(x-1)}` 

`=` `\frac{x^2-2x+1}{2y.(x-1)}`

`=` `\frac{(x-1)^2}{2y.(x-1)}`

`=` `\frac{x-1}{2y}`