Câu hỏi của Trần Văn Dương

Question

Tìm k biết (3k+1)(4k+2)(5k+3)=192

ミ★Ƙαї★彡 · Accepted Answer

$\left(3k+1\right)\left(4k+2\right)\left(5k+3\right)=192$

$\Leftrightarrow60k^3+86k^2+40k+6=192$

$\Leftrightarrow60k^3+86k^2+40k-186=0$

$\Leftrightarrow2\left(30k^2+73k+93\right)\left(k-1\right)=0$

$\Leftrightarrow k=1$

Câu trả lời:

$\left(3k+1\right)\left(4k+2\right)\left(5k+3\right)=192$

$\Leftrightarrow60k^3+86k^2+40k+6=192$

$\Leftrightarrow60k^3+86k^2+40k-186=0$

$\Leftrightarrow2\left(30k^2+73k+93\right)\left(k-1\right)=0$

$\Leftrightarrow k=1$