Question

2^x+2^(x+1)+2^(x-1)=56

Answer 1

2x+2x+2+2x-2=56<->6x=56-<> x= 56/6 ->x= 28/3

Answer 2

$\displaystyle 2^x+2^{x+1}+2^{x-1}=56 \\ 2^x(1+2^1+2^-^1)=56 \\ 2^x\left(1+2+ \frac{1}{2} \right)=56 \\ 2^x \left( 3+ \frac{1}{2} \right)=56 \\ 2^x \left( \frac{6}{2} + \frac{1}{2} \right)=56 \\ 2^x \cdot \frac{7}{2} =56 \\ 2^x=56: \frac{7}{2} \\ 2^x=56 \cdot \frac{2}{7} \\ 2^x= \frac{112}{7} \\ 2^x=16 \\ 2^x=2^4 \\ x=4$