Question

[@Hacker.vn]

• Tìm x thõa mãn 

            a,  \(2^{x-1}+5.2^{x-2}=224\) 

            b,  \(5^{x-2017}+5^{x-2015}=650\)

            c,   \(2^x-2^y=256\left(x>y\right)\)

Answer 1

[Cold Wind]

a) \(2^{x-1}+5\cdot2^{x-2}=224\)

\(2^x:2+5\cdot2^x:4=224\)

\(2^x\left(\frac{1}{2}+\frac{5}{4}\right)=224\)

\(2^x=128\)

\(x=7\)

b) \(5^{x-2017}+5^{x-2015}=650\)

\(5^{x-2015}\left(\frac{1}{25}+1\right)=650\)

\(5^{x-2015}=625\)

\(x=2019\)

c) \(2^x-2^y=256\left(x>y\right)\)

(ko biết)