Đáp án: `A = \frac{-1}{x + 2}`
Giải thích các bước giải:
`A= \frac{2-x}{x+3} - \frac{3-x}{x+2} + \frac{2-x}{x^2 + 5x + 6}`
`A = \frac{( 2 - x )( x + 2 )}{(x+3)( x + 2)} - \frac{( 3- x )(x + 3 )}{(x + 3 )(x+2)} + \frac{2 - x }{(x+ 3 )( x + 2 )}`
`A = \frac{4 - x^2}{( x + 3 )( x + 2 )} - \frac{9 -x^2}{( x + 3 )( x + 2 )} + \frac{2 - x }{( x + 3 )( x + 2)}`
`A = \frac{ 4 - x^2 - ( 9 - x^2 ) + 2 - x }{( x+ 3)( x+2)}`
`A = \frac{ 4 - x^2 - 9 + x^2 + 2 - x}{( x +3)( x + 2)}`
`A = \frac{-x-3}{( x + 3)( x + 2)}`
`A = \frac{ -( x + 3 )}{( x + 3)( x + 2)}`
`A = \frac{-1}{x + 2}`
