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\(3^{-1}.3^n+5.3^{n-1}=162\)
\(\Rightarrow3^{n-1}+5.3^{n-1}=162\)
\(\Rightarrow3^{n-1}\left(1+5\right)=162\)
\(\Rightarrow3^{n-1}.6=162\)
\(\Rightarrow3^{n-1}=162:6=27\)
\(\Rightarrow3^{n-1}=3^3\)
\(\Rightarrow n-1=3\)
\(\Rightarrow n=4\)
\(2008^n=1\Rightarrow n=0\)
\(2^n=1024\Rightarrow2^n=2^{10}\Rightarrow n=10\)
tíc mình nha
\(a,2008^n=1=>n=0.\)
\(b,5^n+5^{n+2}=650\)
\(=>5^n\left(1+5^2\right)=650\)
\(=>5^n.26=650\)
\(=>5^n=650:26\)
tự tính tiếp nhé !!
\(c,2^n=1024=2^{10}=>n=10\)
\(d,3^{n-1}5.3^{n-1}=162\)mình nghĩ đề thiếu !
\(\dfrac{1}{2}+\dfrac{2}{3}+\dfrac{3}{5}\)
\(=\dfrac{15}{30}+\dfrac{20}{30}+\dfrac{18}{30}\)
\(=\dfrac{15+20+18}{30}\)
\(=\dfrac{53}{30}\)
_________________
\(\dfrac{3}{8}+\dfrac{3}{4}+\dfrac{1}{16}\)
\(=\dfrac{12}{32}+\dfrac{24}{32}+\dfrac{2}{32}\)
\(=\dfrac{12+24+2}{32}\)
\(=\dfrac{19}{16}\)
_______________
\(\dfrac{2}{5}+\dfrac{3}{10}+\dfrac{28}{35}+\dfrac{3}{2}\)
\(=\dfrac{2}{5}+\dfrac{3}{10}+\dfrac{4}{5}+\dfrac{3}{2}\)
\(=\dfrac{4}{10}+\dfrac{3}{10}+\dfrac{8}{10}+\dfrac{15}{10}\)
\(=\dfrac{4+3+8+15}{10}\)
\(=\dfrac{30}{10}\)
\(=3\)
câu a đề sai
2n-15=17
=> 2n=17+15
=>2n=32
=> n=5
c,\(2.3^n=162=>3^n=162:2=>3^n=81\)
=>\(n=4\)
d, (7n-11)^3=2^5.5^2+200 = (7n-11)^3=32.25+200
= (7n-11)^3=800 +200 = 1000
câu này đè sai