ok bn

tôi sai rồi :((((

c. 9(x - 3)² - 4(x + 1)²

= 3²(x - 3)² - 2²(x + 1)²

= \(\left[3\left(x-3\right)\right]^2-\left[2\left(x+1\right)\right]^2\)

= (3x - 9)² - (2x + 2)²

= (3x - 9 - 2x - 2)(3x - 9 + 2x + 2)

= (x - 11)(5x - 7)

d. 25x² - \(\dfrac{1}{81}x^2y^2\)

= (5x)² - \(\left(\dfrac{1}{9}xy\right)^2\)

= \(\left(5x-\dfrac{1}{9}xy\right)\left(5x+\dfrac{1}{9}xy\right)\) 

:))))

là số nhiều thì phải

\(\dfrac{32}{80}=\dfrac{4000}{10000}\)

\(\dfrac{72}{400}=\dfrac{1800}{10000}\)

\(\dfrac{425}{5000}=\dfrac{850}{10000}\)

Nice

\(\dfrac{3}{7}.\dfrac{11}{13}-\dfrac{3}{13}.\dfrac{15}{7}.\dfrac{-17}{7}\)

= \(\dfrac{33}{91}-\dfrac{-765}{673}\)

= 1,4993387