Question

Срочно пжжжжж помогите ​

Answer 1

Ответ:

${7}^{x + 1} - 3 \times {7}^{x} = 28 \\ {7}^{x} \times 7 - 3 \times {7}^{x} = 28 \\ {7}^{x} (7 - 3) = 28 \\ {7}^{x} \times 4 = 28 \\ {7}^{x} = 7 \\ x = 1$