\(\left(2x-1\right)^2+\left(x+3\right)^2-5\left(x-7\right)\left(x+7\right)=0\)

<=>\(\left(2x-1\right)^2+\left(x+3\right)^2-5\left(x^2-49\right)=0\)

<=>\(4x^2-4x+1+x^2+6x+9-5x^2+245=0\)

<=>2x+255=0 

<=>2x=-255

<=>x=-255/2

chú thich dấu nhân là . nha

ta có

\(\frac{16.7-5}{16.16+11}\)\(=\frac{7-5}{16+11}=\frac{2}{27}\)

ok đúng 100%

Còn Cách Khác Ko P

còn nhưng dài dòng lắm

0,2xX-\(\frac{7}{5}\)xX=-\(\frac{42}{45}\)

X=0,7777777778

\(-\dfrac{5}{7}\times\dfrac{2}{13}+\dfrac{-5}{7}\times\dfrac{3}{13}-\dfrac{5}{7}\times\dfrac{8}{13}\)

\(=-\dfrac{5}{7}\left(\dfrac{2}{13}+\dfrac{3}{13}+\dfrac{8}{13}\right)\)

\(=-\dfrac{5}{7}\times\dfrac{13}{13}\)

\(=-\dfrac{5}{7}\times1=-\dfrac{5}{7}\)

\(-\dfrac{5}{7}.\dfrac{2}{13}+\dfrac{-5}{7}.\dfrac{3}{13}-\dfrac{5}{7}.\dfrac{8}{13}\)

\(=-\dfrac{10}{91}-\dfrac{15}{91}-\dfrac{40}{91}\)

\(=\dfrac{-10-15-40}{91}\)

\(=-\dfrac{65}{91}=-\dfrac{5}{7}\)

\(\dfrac{-5}{7}.\dfrac{2}{13}+\left(\dfrac{-5}{7}\right).\dfrac{3}{13}-\dfrac{5}{7}.\dfrac{8}{13}\)

\(=\dfrac{5}{7}.\left(\dfrac{-2}{13}+\dfrac{-3}{13}-\dfrac{8}{13}\right)\)

\(=\dfrac{5}{7}.\left(-1\right)\)

\(=-\dfrac{5}{7}\)

\(#PaooNqoccc\)