Question

tìm x,y biết:

a, 2^x + 624 = 5^y

b, 2^x + 2^x+1 + 2^{x + 2} =28

Answer 1

\(2^x\)+\(2^x\).2+\(2^x\).\(2^2\)=28

\(2^x\)(1+2+4)=28

\(2^x\).7=28

\(2^x\)=4

\(2^2\)=4

x=4

Answer 2

a,

b, \(2^x+2^{x+1}+2^{x+2}=28\)
\(\Leftrightarrow2^x+2^x.2+2^x.2^2=28\)
\(\Leftrightarrow2^x\left(1+2+4\right)=28\)
\(\Leftrightarrow2^x.7=28\)
\(\Leftrightarrow2^x=4\)
\(\Leftrightarrow2^x=2^2\)
=> x = 2