Question

$2 {}^{x} +2 {}^{x-1} +2 {}^{x=2} = 7^x-6 \times 7 {}^{x-1} -5 \times 7 {}^{x-2}$
Помогите пожалуйста
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Answer 1

$2^{x}+2^{x-1}+2^{x-2} =7^{x}-6*7^{x-1}-5*7^{x-2}\\\\2^{x-2} (2^{2}+2+1)=7^{x-2} (7^{2}-6*7-5)\\\\2^{x-2}*7=7^{x-2}*2 \ |:7^{x-2} \\\\(\frac{2}{7})^{x-2}=\frac{2}{7}\\\\x-2=1\\\\\boxed{x=3}$