Question

tìm x 

7^2x+1-5.7²=49.2

Answer 1

\(7^{2x+1}-5.7^2=49.2\)

\(7^{2x}.7-5.7^2=98\)

\(7.\left(7^{2x}-5.7\right)=98\)

\(7^{2x}-35=98:7\)

\(7^{2x}-35=14\)

\(7^{2x}=14+35\)

\(7^{2x}=49\)

\(7^{2x}=7^2\)

\(2x=2\)

\(x=1\)

Answer 2

\(7^{2x+1}-245=98\)

=> \(7^{2x+1}=98+245=343=7^3\)

=>\(2x+1=3\)

=>\(2x=2\)

=>\(x=1\)

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Answer 3

7^(2x+1)-245=98

7^2x+1=98+245=343=7^3

2x+1=3

2x=3-1

2x=2

x=2:2

x=1

Answer 4

\(7^{2x+1}-5.7^2=49.2\)

\(7^{2x}.7-5.7^2=98\)

\(7.\left(7^{2x}-5.7\right)=98\)

\(7^{2x}-35=98:7\)

\(7^{2x}-35=14\)

\(\Rightarrow7^{2x}=49\)

\(\Rightarrow7^{2x}=7^2\)

\(\Rightarrow2x=2\)

\(\Rightarrow x=1\)