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\(\frac{7.9+14.27+21.36}{21.27+42.81+63.108}=\frac{7.3^2+2.7.3^3+3.7.2^2.3^2}{3.7.3^3+2.3.7.3^4+7.3^2.2^2.3^3}=\frac{7.3^2+2.7.3^3+3^3.7.2^2}{3^4.7+2.7.3^5+2^2.7.3^5}\)\(=\frac{7.3^2\left(1+2.3+2^2.3\right)}{3^4.7\left(1+2.3+2^2.3\right)}=\frac{7.3^2}{3^4.7}=\frac{1}{3^2}=\frac{1}{9}\)
\(\left(\frac{2}{3}.x+\frac{5}{6}\right).\left(\frac{3}{4}.x-\frac{27}{8}\right)=0\)
\(\Rightarrow\orbr{\begin{cases}\frac{2}{3}.x+\frac{5}{6}=0\\\frac{3}{4}.x-\frac{27}{8}=0\end{cases}}\Rightarrow\orbr{\begin{cases}\frac{2}{3}.x=\frac{-5}{6}\\\frac{3}{4}.x=\frac{27}{8}\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{-5}{4}\\x=\frac{9}{2}\end{cases}}\)
Vậy \(x=\frac{-5}{4}\) hoặc \(x=\frac{9}{2}\).
Học tốt
\(\left(\frac{2}{3}.x+\frac{5}{6}\right).\left(\frac{3}{4}.x-\frac{27}{8}\right)=0=>\orbr{\begin{cases}\left(\frac{3}{4}.x-\frac{27}{8}\right)=0\\\left(\frac{2}{3}.x+\frac{5}{6}\right)=0\end{cases}}\)
\(\orbr{\begin{cases}\frac{2}{3}.x=0-\frac{5}{6}\\\frac{3}{4}.x=0+\frac{27}{8}\end{cases}}=>\orbr{\begin{cases}\frac{2}{3}.x=-\frac{5}{6}\\\frac{3}{4}.x=\frac{27}{8}\end{cases}}=>\orbr{\begin{cases}x=-\frac{5}{6}:\frac{2}{3}\\x=\frac{27}{8}:\frac{3}{4}\end{cases}}=>\orbr{\begin{cases}x=-\frac{5}{4}\\x=\frac{9}{2}\end{cases}}\)
vậy \(\orbr{\begin{cases}x=-\frac{5}{4}\\x=\frac{9}{2}\end{cases}}\)
3. Ta có:
(x+1) + (x+2) +... + (x+100) = 9050
(x+x+x+ ...+x+x) +..+ (1+2+3+..+100)= 9050
100.x +5050 = 9050
100.x =4000
\(\Rightarrow x=40\)
Vậy ...
\(1+2+3+..+100=\dfrac{\left(1+100\right).100}{2}=5050\)
Vầy đó bạn :))
4.x:17= 0
4.x=0:17
4.x=0
x=0:4
x=0
7.x-8=713
7.x=713+8
7.x=721
x=721:7=103
x-3=0:8
x.3=0
x=0:3
x=0