Question

Tìm x,y thuộc N biết:

a) 2^x+1. 3^y =12^x

b) 10^x : 5^y =20^y

c) -3.3^x + 5.3^x  =162

Answer 1

\(2^{x-1}=3^{y-x}\Rightarrow x-1=y-x=0\Rightarrow\hept{\begin{cases}x=1\\y=1\end{cases}}\)

Answer 2

\(2^{x+1}.3^y=12^x\Rightarrow2^{x+1}.3^y=2^{2x}.3y\Rightarrow\frac{2^{2x}}{2^{x+1}}=\frac{3^y}{3^x}\Rightarrow2^{2x-x-1}=3^{y-x}\)