\(4-\left|5x-2\right|-\left|3y+12\right|\)
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KK
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19 tháng 7 2017
\(\)bài nào có MIN or MAX thì mk làm,mk ko làm thì có nghĩa là ko có nha
\(D=\left|4x-3\right|+\left|5y+7,5\right|+17,5\)
\(\left\{{}\begin{matrix}\left|4x-3\right|\ge0\\\left|5y+7,5\right|\ge0\end{matrix}\right.\)
\(\Rightarrow\left|4x-3\right|+\left|5y+7,5\right|\ge0\)
\(\Rightarrow\left|4x-3\right|+\left|5y+7,5\right|+17,5\ge17,5\)
Dấu "=" xảy ra khi:
\(\left\{{}\begin{matrix}\left|4x-3\right|=0\Rightarrow4x=3\Rightarrow x=\dfrac{3}{4}\\\left|5y+7,5\right|=0\Rightarrow5y=-7,5\Rightarrow y=-1,5\end{matrix}\right.\)
\(\Rightarrow MIN_D=17,5\) khi \(x=\dfrac{3}{4};y=-1,5\)
\(E=4-\left|5x-2\right|-\left|3y+12\right|\)
\(\left\{{}\begin{matrix}\left|5x-2\right|\ge0\\\left|3y+12\right|\ge0\end{matrix}\right.\)
\(\Rightarrow E=4-\left|5x-2\right|-\left|3y+12\right|\le4\)
Dấu "=" xảy ra khi:
\(\left\{{}\begin{matrix}\left|5x-2\right|=0\Rightarrow5x=2\Rightarrow x=\dfrac{2}{5}\\\left|3y+12\right|=0\Rightarrow3y=-12\Rightarrow y=-4\end{matrix}\right.\)
\(\Rightarrow MAX_E=4\) khi \(x=\dfrac{2}{5};y=-4\)
15 tháng 10 2017
\(A=4-\left|5x-2\right|-\left|3y+12\right|\le4\)
Dấu "=" xảy ra khi:
\(\left\{{}\begin{matrix}5x-2=0\\3y+12=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{2}{5}\\y=-4\end{matrix}\right.\)
Vậy \(max_A=4\) khi \(\left\{{}\begin{matrix}x=\dfrac{2}{5}\\y=-4\end{matrix}\right.\)
8 tháng 1 2021
1)
HPT \(\Leftrightarrow\left\{{}\begin{matrix}15x-6y=-27\\8x+6y=4\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}2y=5x+9\\23x=-23\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=-1\\y=2\end{matrix}\right.\)
Vậy \(\left(x;y\right)=\left(-1;2\right)\)
2)
HPT \(\Leftrightarrow\left\{{}\begin{matrix}2x+y=4\\2x+4y=10\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}-3y=-6\\x=5-2y\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}y=2\\x=1\end{matrix}\right.\)
Vậy \(\left(x;y\right)=\left(1;2\right)\)
3)
HPT \(\Leftrightarrow\left\{{}\begin{matrix}4x+6y=14\\3x+6y=12\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=2\\2y=4-x\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=2\\y=1\end{matrix}\right.\)
Vậy \(\left(x;y\right)=\left(2;1\right)\)
4)
HPT \(\Leftrightarrow\left\{{}\begin{matrix}5x+6y=17\\54x-6y=42\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}59x=59\\y=9x-7\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=1\\y=2\end{matrix}\right.\)
Vậy \(\left(x;y\right)=\left(1;2\right)\)
12 tháng 1 2019
a) Đề sai nha bạn :) mấy dấu cộng bạn phỉa chuyển thành dấu nhân nhé
\(A=\left(2+1\right)\left(2^2+1\right)...\left(2^{256}+1\right)+1\)
\(A=\left(2-1\right)\left(2+1\right)\left(2^2+1\right)...\left(2^{256}+1\right)+1\)
\(A=\left(2^2-1\right)\left(2^2+1\right)...\left(2^{256}+1\right)+1\)
\(A=\left(2^{256}-1\right)\left(2^{256}+1\right)+1\)
\(A=2^{512}-1+1\)
\(A=2^{512}\)
12 tháng 1 2019
b . ( 5x - 3y + 4z )( 5x - 3y - 4z ) = ( 5x - 3y )^2 - ( 4z )^2 = 25x^2 - 30xy + 9y^2 - 16z^2 = 25( y^2 + z^2 ) - 30xy + 9y^2 - 16z^2 = 9z^2 + 34y^2 - 30xy ( 1 )
( 3x - 5y )^2 = 9x^2 - 30xy + 25y^2 = 9( y^2 + z^2 ) - 30xy + 25y^2 = 34y^2 + 9z^2 - 30xy ( 2 )
Tu ( 1 ) va ( 2 ) => dpcm