Question

tìm x, y biết: 8.2^3x.7^y = 56^2x.5^x-1

Answer 1

\(8.2^{3x}.7^y=56^{2x}.5^{x-1}\)

\(2^3.2^{3x}.7^y=7^{2x}.8^{2x}.5^{x-1}\)

\(2^{3+3x}.7^y=7^{2x}.2^{6x}.5^{x-1}\)

\(7^{2x}:7^y=2^{6x}:2^{3+3x}.5^{x-1}\)

\(7^{2x-y}=2^{6x-3-3x}.5^{x-1}\)

\(7^{2x-y}=2^{3x-3}.5^{x-1}\)

\(7^{2x-y}=2^{3x}:8.5^x:5\)

\(7^{2x-y}=8^x.5^x:40\)

\(7^{2x-y}=40^x:40\)

\(7^{2x-y}=40^{x-1}\)

\(\Rightarrow x=y=1\)