Câu hỏi của Velvet Red

Question

$3^{x+1}-3^x=162$

$\left(1-x\right)^3=216$

$5^{x+1}-2.5^x=375$

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✿✿❑ĐạT̐®ŋɢย❐✿✿ · Accepted Answer

a) $3^{x+1}-3^x=162$

$\Leftrightarrow3^x.\left(3-1\right)=162$

$\Leftrightarrow3^x.2=162$

$\Leftrightarrow3^x=162:2=81$

$\Leftrightarrow3^x=3^4$

$\Leftrightarrow x=4$

b) $\left(1-x\right)^3=216$

$\Leftrightarrow\left(1-x\right)^3=6^3$

$\Leftrightarrow1-x=6$

$\Leftrightarrow x=1-6$

$\Leftrightarrow x=-5$

c) $5^{x+1}-2.5^x=375$

$\Leftrightarrow5^x.\left(5-2\right)=375$

$\Leftrightarrow5^x.3=375$

$\Leftrightarrow5^x=375:3=125$

$\Leftrightarrow5^x=5^3$

$\Leftrightarrow x=3$Câu trả lời: a) $3^{x+1}-3^x=162$