Question

Решите уравнение:
$7 ^{x+2}-2*7 ^{x+1}+5*7 ^{x}=280$

Answer 1

$7^{x} *7^{2} -2*7^{x} *7+5*7^{x}=280 \ (49-14+5)*7^{x}=280 \ 40*7^{x}=280 \ 7^{x}=7 \ x=1$