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Đặt \(\dfrac{x}{2}=\dfrac{y}{3}=k\)
Ta có :
\(\left\{{}\begin{matrix}x=2k\\y=3k\end{matrix}\right.\)
\(\Rightarrow xy=54\Leftrightarrow2k.3k=54\)
\(\Rightarrow6k^2=54\)
\(\Rightarrow k^2=54:6\)
\(\Rightarrow k^2=9\)
\(\Rightarrow k^2=\left(\pm3\right)^2\)
\(\Rightarrow\left\{{}\begin{matrix}x=2.\left(\pm3\right)=\left(\pm6\right)\\y=3.\left(\pm3\right)=\left(\pm9\right)\end{matrix}\right.\)
Vậy \(\left(x;y\right)\in\left\{\left(6;9\right),\left(-6;-9\right)\right\}\)
Mình có thấy cái đề bài đâu nhỉ????????
\(8,64\times46+52\times8,64+17,28\)
\(=8,64\times46+52\times8,64+8,64\times2\)
\(=8,64\times\left(46+52+2\right)\)
\(=8,64\times100=864\)
\(26+5x=3x+56\)
\(\Rightarrow5x-3x=56-26\)
\(\Rightarrow2x=30\)
\(\Rightarrow x=30:2\)
\(\Rightarrow x=15\)
Vậy \(x=15\)
Tớ không thấy đề bài cậu ơi!
\(24.\left[18-\left(3^2-2\right)^2\right]\)
\(=24.\left[18-\left(9-2\right)^2\right]\)
\(=24.\left[18-7^2\right]\)
\(=24.\left[18-49\right]\)
\(=24.-31=-744\)
`987`\(\times34+65\times987+978+9\)
\(=987\times\left(34+65\right)+978+9\)
\(=987\times99+978+9\)
\(=97713+978+9\)
\(=98691+9=98700\)
Hbth cop AI => ghi TK ah!
\(Ư\left(15\right)=\left\{1;3;5;15\right\}\)
Mở rộng : \(Ư\left(15\right)=\left\{\pm1;\pm3;\pm5;\pm15\right\}\)
\(81:3^2+5\times4^2-7\times3^2\)
\(=81:9-5\times16-7\times9\)
\(=9-80-63\)
\(=-71-63=-134\)