Question

tìm số tự nhiên n,biết a)4^n =16

b) 4×4^n=256

c)2×n^2=32

d)n^2=4

e)3^n=9

Answer 1

\(a,4^n=16\\ \Leftrightarrow4^n=4^2\\ \Leftrightarrow n=2\\ b,4\times4^n=256\\ \Leftrightarrow4^n=64\\ \Leftrightarrow4^n=4^3\\ \Leftrightarrow n=3\\ c,2\times n^2=32\\ \Leftrightarrow n^2=16\\ \Leftrightarrow n=4\\ d,n^2=4\\ \Leftrightarrow n^2=2^2\\ \Leftrightarrow n=2\\ e,3^n=9\\ \Leftrightarrow3^n=3^2\\ \Leftrightarrow n=2\)

Answer 2

a). \(4^n=16\)

\(4^n=4^2\)

\(\Rightarrow n=2\)

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b). \(4\times4^n=256\)

\(4^n=256:4\)

\(4^n=64\)

\(4^n=4^3\)

\(\Rightarrow n=3\)

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c). \(2\times n^2=32\)

\(n^2=32:2\)

\(n^2=16\)

\(n^2=4^2\)

\(\Rightarrow n=4\)

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d). \(n^2=4\)

\(n^2=2^2\)

\(\Rightarrow n=2\)

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e). \(3^n=9\)

\(3^n=3^2\)

\(\Rightarrow n=2\)