# Exercise ID319

Algebra → Exponential equations and inequalities → Exponential equations
[Level: ] [Number of helps: 0] [Number of pictures: 0] [Number of steps: 7] [Number of characters: 0]

Evaluate the following expression:

${7}^{x+2}+2×{7}^{x-1}=345\phantom{\rule{0ex}{0ex}}$

${7}^{x}×{7}^{2}+2×{7}^{x}×{7}^{-1}=345\phantom{\rule{0ex}{0ex}}$ ${7}^{x}×\left({7}^{2}+\frac{2}{7}\right)=345\phantom{\rule{0ex}{0ex}}$ ${7}^{x}×\left(\frac{343+2}{7}\right)=345\phantom{\rule{0ex}{0ex}}$ ${7}^{x}×\frac{345}{7}=345\phantom{\rule{0ex}{0ex}}$ ${7}^{x}=\frac{345×7}{345}\phantom{\rule{0ex}{0ex}}$ ${7}^{x}=7\phantom{\rule{0ex}{0ex}}$ $x=1\phantom{\rule{0ex}{0ex}}$
$x=1\phantom{\rule{0ex}{0ex}}$