N=1/6.5/9+5/9.2/7+1/9.5/7-5/9.3/7
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a: \(3^n\cdot3^4\cdot\dfrac{1}{9}=3^7\)
\(\Leftrightarrow3^n\cdot3^2=3^7\)
=>n+2=7
hay n=5
b: \(\Leftrightarrow2^n\cdot\left(\dfrac{1}{2}+4\right)=9\cdot2^5\)
\(\Leftrightarrow2^n=9\cdot2^5:\dfrac{9}{2}=9\cdot\dfrac{2}{9}\cdot2^5=2^6\)
hay n=6
1.1
x=(3/5)^7:(3/5)^5=(3/5)^7-5=(3/5)62=6/5=1,2
1.2
x=5+7/10+3/10=5+10/10=5+1=6
1.3
x=\(\frac{18}{23}\) :\(\frac{6}{7}\) =\(\frac{18}{23}\) . \(\frac{7}{6}\) = \(\frac{21}{23}\)
\(a,\frac{2^{10}.3^{10}-2^{10}.3^9}{2^9.3^{10}}=\frac{2^{10}.3^9\left(3-1\right)}{2^9.3^{10}}=\frac{2.2}{3}=\frac{4}{3}\)
\(b,\frac{5^{11}.7^{12}+5^{11}.7^{11}}{5^{12}.7^{12}+9.5^{11}.7^{11}}=\frac{5^{11}.7^{11}\left(7+1\right)}{5^{11}.7^{11}\left(5.7+9\right)}=\frac{8}{44}=\frac{2}{11}\)
học tốt
a)
\(\frac{2^{10}.3^{10}-2^{10}.3^9}{2^9.3^{10}}\)
\(=\frac{2^{10}.3^9\left(3-1\right)}{2^9.3^{10}}\)
\(=\frac{2.2}{3}\)
\(=\frac{4}{3}\)
b)
\(\frac{5^{11}.7^{12}+5^{11}.7^{11}}{5^{12}.7^{12}+9.5^{11}.7^{11}}\)
\(=\frac{5^{11}.7^{11}\left(7+1\right)}{5^{11}.7^{11}\left(5.7+9\right)}\)
\(=\frac{8}{35+9}\)
\(=\frac{8}{44}\)
\(=\frac{2}{11}\)
A = \(\dfrac{5}{9}\cdot\left(\dfrac{1}{7}+\dfrac{1}{7}+\dfrac{3}{7}\right)\)
=\(\dfrac{5}{9}\cdot\dfrac{5}{7}=\dfrac{25}{63}\)