Tìm x,y:
lx+2l + (y+5)2\(\le0\)
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NC
16 tháng 8 2020
Bài 1:
a) \(\hept{\begin{cases}\left(x-\frac{2}{5}\right)^{2010}\ge0\left(\forall x\right)\\\left(y+\frac{3}{7}\right)^{468}\ge0\left(\forall y\right)\end{cases}}\Rightarrow\left(x-\frac{2}{5}\right)^{2010}+\left(y+\frac{3}{7}\right)^{468}\ge0\left(\forall x,y\right)\)
Kết hợp với đề bài, dấu "=" xảy ra khi:
\(\hept{\begin{cases}\left(x-\frac{2}{5}\right)^{2010}=0\\\left(y+\frac{3}{7}\right)^{468}=0\end{cases}}\Rightarrow\hept{\begin{cases}x=\frac{2}{5}\\y=-\frac{3}{7}\end{cases}}\)
b) \(\hept{\begin{cases}\left(x+0,7\right)^{84}\ge0\left(\forall x\right)\\\left(y-6,3\right)^{262}\ge0\left(\forall y\right)\end{cases}\Rightarrow}\left(x+0,7\right)^{84}+\left(y-6,3\right)^{262}\ge0\left(\forall x,y\right)\)
Kết hợp với đề bài, dấu "=" xảy ra khi:
\(\hept{\begin{cases}\left(x+0,7\right)^{84}=0\\\left(y-6,3\right)^{262}=0\end{cases}}\Rightarrow\hept{\begin{cases}x=-0,7\\y=6,3\end{cases}}\)
c) \(\hept{\begin{cases}\left(x-5\right)^{88}\ge0\left(\forall x\right)\\\left(x+y+3\right)^{496}\ge0\left(\forall x,y\right)\end{cases}\Rightarrow}\left(x-5\right)^{88}+\left(x+y+3\right)^{496}\ge0\left(\forall x,y\right)\)
Kết hợp với đề bài, dấu "=" xảy ra khi:
\(\hept{\begin{cases}\left(x-5\right)^{88}=0\\\left(x+y+3\right)^{496}=0\end{cases}}\Rightarrow\hept{\begin{cases}x=5\\y=-8\end{cases}}\)
NC
16 tháng 8 2020
Bài 2:
Theo giả thiết ta có thể suy ra: \(x>y\)
Ta có: \(2^x-2^y=224\)
\(\Leftrightarrow2^y\left(2^{x-y}-1\right)=224=32.7=2^5.7\)
Mà \(2^{x-y}-1\) luôn lẻ với mọi x,y nguyên
=> \(\hept{\begin{cases}2^{x-y}-1=7\\2^y=2^5\end{cases}\Leftrightarrow}\hept{\begin{cases}2^{x-y}=8=2^3\\y=5\end{cases}}\Leftrightarrow\hept{\begin{cases}x=8\\y=5\end{cases}}\)
LT
1
13 tháng 8 2019
a) 8 - |x + 2| = 5
-|x + 2| = 5 - 8
-|x + 2| = -3
|x + 2| = 3
x + 2 = 3; -3
x + 2 = 3 hoặc x + 2 = -3
x = 3 - 2 x = -3 - 2
x = 1 x = -5
=> x = 1 hoặc x = -5
15 tháng 9 2021
a) \(x^2+\left(y-\dfrac{1}{10}\right)^4=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=0\\y-\dfrac{1}{10}=0\end{matrix}\right.\)( do \(x^2\ge0,\left(y-\dfrac{1}{10}\right)^4\ge0\))
\(\Leftrightarrow\left\{{}\begin{matrix}x=0\\y=\dfrac{1}{10}\end{matrix}\right.\)
b) \(\left(\dfrac{1}{2}.x-5\right)^{20}+\left(y^2-\dfrac{1}{4}\right)^{10}\le0\)
\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{1}{2}x-5=0\\y^2-\dfrac{1}{4}=0\end{matrix}\right.\)( do \(\left(\dfrac{1}{2}x-5\right)^{20}\ge0,\left(y^2-\dfrac{1}{4}\right)^{10}\ge0\))
\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{1}{2}x=5\\y^2=\dfrac{1}{4}\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}x=10\\y=\pm\dfrac{1}{2}\end{matrix}\right.\)
15 tháng 9 2021
\(a,\Leftrightarrow\left\{{}\begin{matrix}x=0\\y-\dfrac{1}{10}=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=0\\y=\dfrac{1}{10}\end{matrix}\right.\\ b,\left\{{}\begin{matrix}\left(\dfrac{1}{2}x-5\right)^{20}\ge0\\\left(y^2-\dfrac{1}{4}\right)^{10}\ge0\end{matrix}\right.\Leftrightarrow\left(\dfrac{1}{2}x-5\right)^{20}+\left(y^2-\dfrac{1}{4}\right)^{10}\ge0\)
Mà \(\left(\dfrac{1}{2}x-5\right)^{20}+\left(y^2-\dfrac{1}{4}\right)^{10}\le0\)
\(\Leftrightarrow\left(\dfrac{1}{2}x-5\right)^{20}+\left(y^2-\dfrac{1}{4}\right)^{10}=0\\ \Leftrightarrow\left\{{}\begin{matrix}\dfrac{1}{2}x=5\\y^2=\dfrac{1}{4}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=10\\y=\pm\dfrac{1}{2}\end{matrix}\right.\)
28 tháng 9 2021
a) \(\left|3x-\dfrac{1}{2}\right|+\left|\dfrac{1}{4}y+\dfrac{3}{5}\right|=0\)
Do \(\left|3x-\dfrac{1}{2}\right|,\left|\dfrac{1}{4}y+\dfrac{3}{5}\right|\ge0\forall x,y\)
\(\Rightarrow\left\{{}\begin{matrix}3x-\dfrac{1}{2}=0\\\dfrac{1}{4}y+\dfrac{3}{5}=0\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}x=\dfrac{1}{6}\\y=-\dfrac{12}{5}\end{matrix}\right.\)
b) \(\left|\dfrac{3}{2}x+\dfrac{1}{9}\right|+\left|\dfrac{5}{7}y-\dfrac{1}{2}\right|\le0\)
Do \(\left|\dfrac{3}{2}x+\dfrac{1}{9}\right|,\left|\dfrac{5}{7}y-\dfrac{1}{2}\right|\ge0\forall x,y\)
\(\Rightarrow\left\{{}\begin{matrix}\dfrac{3}{2}x+\dfrac{1}{9}=0\\\dfrac{5}{7}y-\dfrac{1}{2}=0\end{matrix}\right.\)\(\Rightarrow\left\{{}\begin{matrix}x=-\dfrac{2}{27}\\y=\dfrac{7}{10}\end{matrix}\right.\)
10 tháng 7 2018
Vì \(\left(\frac{1}{2}x-5\right)^{10}\ge0\)và \(\left(y^2-\frac{1}{4}\right)^{20}\ge0\)
nên \(\left(\frac{1}{2}x-5\right)^{10}+\left(y^2-\frac{1}{4}\right)^{20}=0\)
<=>\(\hept{\begin{cases}\frac{1}{2}x-5=0\\y^2-\frac{1}{4}=0\end{cases}}\)<=>\(\hept{\begin{cases}x=10\\y=\pm\frac{1}{2}\end{cases}}\)
DQ
12 tháng 2 2020
Ta có:\(\hept{\begin{cases}\left\{\frac{1}{2}x-5\right\}^{10}\ge0\forall x\\\left\{y^2-\frac{1}{4}\right\}^{20}\ge0\forall y\end{cases}}\)
Mà \(\left\{\frac{1}{2}x-5\right\}^{10}+\left\{y^2-\frac{1}{4}\right\}^{20}\le0\)
\(\Rightarrow\left\{\frac{1}{2}x-5\right\}^{10}+\left\{y^2-\frac{1}{4}\right\}^{20}=0\)
\(\Leftrightarrow\hept{\begin{cases}\left\{\frac{1}{2}x-5\right\}^{10}=0\\\left\{y^2-\frac{1}{4}\right\}^{20}=0\end{cases}\Leftrightarrow\hept{\begin{cases}\frac{1}{2}x-5=0\\y^2-\frac{1}{4}=0\end{cases}\Leftrightarrow}\hept{\begin{cases}\frac{1}{2}x=5\\y^2=\frac{1}{4}\end{cases}\Leftrightarrow}\hept{\begin{cases}x=10\\y=\pm\frac{1}{2}\end{cases}}}\)
Vậy \(x=10;y=\pm\frac{1}{2}\)
14 tháng 9 2017
Xét \(\left(\frac{1}{2}x-5\right)^{20}\ge0\)
\(\left(y^2-\frac{1}{4}\right)^{10}\ge0\)
\(\Rightarrow\) \(\left(\frac{1}{2}x-5\right)^{20}+\left(y^2-\frac{1}{4}\right)^{10}\ge0\)
mà \(\left(\frac{1}{2}x-5\right)^{20}+\left(y^2-\frac{1}{4}\right)^{10}=0\)
\(\Leftrightarrow\hept{\begin{cases}\frac{1}{2}x-5=0\\y^2-\frac{1}{4}=0\end{cases}}\)
\(\Rightarrow\hept{\begin{cases}\frac{1}{2}x=5\\y^2=\frac{1}{4}\end{cases}}\)
\(\Rightarrow\hept{\begin{cases}x=10\\y=\pm\frac{1}{2}\end{cases}}\)
Vì
\(\left|x+2\right|\ge0\)
\(\left(y+5\right)^2\ge0\)
\(\Rightarrow\left|x+2\right|+\left(y+5\right)^2\ge0\)
Mà để \(\left|x+2\right|+\left(y+5\right)^2\le0\Rightarrow\orbr{\begin{cases}\left|x+2\right|=0\\\left(y+5\right)^2=0\end{cases}\Rightarrow\orbr{\begin{cases}x=-2\\y=-5\end{cases}}}\)
Vậy \(x=-2;y=-5\)
Vì |x+2| +(y+5)2 \(\ge\)0
Mà ......(đề)......
Nên |x+2| + (y+5)2 =0
Lại có |x+2| \(\ge0\) ; \(\left(y+5\right)^2\ge0\)
\(\Rightarrow\hept{\begin{cases}\left|x+2\right|=0\\\left(y+5\right)^2=0\end{cases}}\Rightarrow\hept{\begin{cases}x+2=0\\y+5=0\end{cases}}\Rightarrow\hept{\begin{cases}x=-2\\y=-5\end{cases}}\)