Question

3^1-x=9

2^x-1+2^x=12

Answer 1

$1) {3}^{1 - x} = 9$

${3}^{1 - x} = {3}^{2}$

$1 - x = 2$

$- x = 2 - 1$

$- x = 1 \: | \times ( - 1)$

$x = - 1$

$2) {2}^{x - 1} + {2}^{x} = 12$

${2}^{x - 1} (1 + 2) = 12$

${2}^{x - 1} \times 3 = 12 \: | \div 3$

${2}^{x - 1} = 4$

${2}^{x - 1} = {2}^{2}$

$x - 1 = 2$

$x = 2 + 1$

$x = 3$