1~~~~\Rightarrow~~~x-1<1;~~~~x<2\\\\\boxed{x\in (-\infty;2)}" alt="7^x-2^{x+2}<5\cdot 7^{x-1}-2^{x-1}}~~~~|:2^{x-1}\\\\\dfrac{7\cdot 7^{x-1}}{2^{x-1}}-\dfrac{2^3\cdot 2^{x-1}}{2^{x-1}}<\dfrac{5\cdot 7^{x-1}}{2^{x-1}}-\dfrac{2^{x-1}}{2^{x-1}}\\\\7\cdot\Big(\dfrac 72\Big)^{x-1}-8<5\cdot \Big(\dfrac 72\Big)^{x-1}-1\\\\7\cdot\Big(\dfrac 72\Big)^{x-1}-5\cdot \Big(\dfrac 72\Big)^{x-1}<8-1\\\\2\cdot\Big(\dfrac 72\Big)^{x-1}<7;~~~~\Leftrightarrow~~~~~\Big(\dfrac 72\Big)^{x-1}<\dfrac 72\\\\\dfrac 72>1~~~~\Rightarrow~~~x-1<1;~~~~x<2\\\\\boxed{x\in (-\infty;2)}" align="absmiddle" class="latex-formula">
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
Метод интервалов для неравенства

+++++++++ [1] ------------ [2] ++++++++ > x
x ∈ [1; 2]