thực hiện tính trừ

B

baochau15

Last edited by a moderator:
C

chonhoi110

Ý bạn đề là thế này:
$\dfrac{4(x+3)^2}{(3x+5)^2 - 4x^2 }-\dfrac{x^2 -25}{9x^2 - ( 2x+5)^2}-\dfrac{ (2x+3)^2 - x^2}{ (4x+15)^2 - x^2}$
$=\dfrac{4(x+3)^2}{(3x+5-2x)(3x+5+2x) }-\dfrac{x^2-25}{(3x-2x-5)(3x+2x+5)}-\dfrac{ (2x+3-x)(2x+3+x)}{ (4x+15-x)(4x+15+x)}$
$=\dfrac{4(x+3)^2}{(x+5)(5x+5) }-\dfrac{(x-5)(x+5)}{5(x-5)(x+1)}-\dfrac{ 3(x+3)(x+1)}{ 15(x+5)(x+3)}$
$=\dfrac{4(x+3)^2}{5(x+5)(x+1) }-\dfrac{(x+5)}{5(x+1)}-\dfrac{ (x+1)}{ 5(x+5)}$
$=\dfrac{4(x+3)^2}{5(x+5)(x+1) }-\dfrac{(x+5)^2}{5(x+1)(x+5)}-\dfrac{ (x+1)^2}{ 5(x+5)(x+1)}$
$=\dfrac{4(x+3)^2-(x+5)^2-(x+1)^2}{5(x+5)(x+1)}$
$=\dfrac{2x^2+12x+10}{5(x+5)(x+1)}$
$=\dfrac{2(x+1)(x+5)}{5(x+5)(x+1)}$
$=\dfrac{2}{5}$
 
Top Bottom