Tìm x để : A= 2x-2/x+2 đạt GTNN.Tìm GTNN đó
Ghi cả câu trả lời mk tick cho
Đang cần gấp😍😍
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PT
1
17 tháng 9 2018
Theo đề ra ta có :
p + e + n = 52
Mà n = 12
=> p + e = 52 - 12
=> p + e = 40
Mà p = e => 2p = 40
=> p = e = 20
=> Tên nguyên tố x là : Canxi; kí hiệu : Ca
Hok tốt nha bn!!
17 tháng 6 2022
a: \(\Leftrightarrow\left(x+2\right)\left(x-2\right)⋮x^2-7\)
\(\Leftrightarrow x^2-7\in\left\{1;-1;3;-3\right\}\)
hay \(x\in\left\{2\sqrt{2};-2\sqrt{2};\sqrt{6};-\sqrt{6};\sqrt{10}-\sqrt{10};2;-2\right\}\)
b: \(\Leftrightarrow2+2+2+...+x=2002\)
\(\Leftrightarrow2\left(\dfrac{x-2}{2}+1\right)=2002\)
\(\Leftrightarrow\left(x-2\right)\cdot\dfrac{1}{2}+1=1001\)
=>1/2(x-2)=1000
=>x-2=2000
hay x=2002
HN
1
14 tháng 1 2018
ta có:/3x-3/\(\ge\)0;//x-4/-3/\(\ge\)0 =>/3x-3/+//x-4/-3/ \(\ge\)0 =>a\(\ge\)0 => gtnn của a=0;
để a có gtnn = 0 thì
\(\hept{\begin{cases}\left|3x-3\right|=0\\\left|x-4\right|-3=0\end{cases}}\)=>\(\hept{\begin{cases}3x-3=0\\\left|x-4\right|=3\end{cases}}\)\(\hept{\begin{cases}3x=3\\x-4=3\\x-4=-3\end{cases}}\)=>\(\hept{\begin{cases}x=1\\x=7\\x=1\end{cases}}\)
Vậy x\(\in\)(1;7)
DM
1
NN
27 tháng 11 2017
a) \(\dfrac{2}{x+3}+\dfrac{1}{x}\) MTC: \(x\left(x+3\right)\)
\(=\dfrac{2x}{x\left(x+3\right)}+\dfrac{x+3}{x\left(x+3\right)}\)
\(=\dfrac{2x+x+3}{x\left(x+3\right)}\)
\(=\dfrac{3x+3}{x\left(x+3\right)}\)
b) \(\dfrac{x+1}{2x-2}+\dfrac{-2x}{x^2-1}\)
\(=\dfrac{x+1}{2\left(x-1\right)}+\dfrac{-2x}{\left(x-1\right)\left(x+1\right)}\) MTC: \(2\left(x-1\right)\left(x+1\right)\)
\(=\dfrac{\left(x+1\right)\left(x+1\right)}{2\left(x-1\right)\left(x+1\right)}+\dfrac{-2x.2}{2\left(x-1\right)\left(x+1\right)}\)
\(=\dfrac{\left(x+1\right)^2-4x}{2\left(x-1\right)\left(x+1\right)}\)
\(=\dfrac{\left(x+1\right)-4x}{2\left(x-1\right)}\)
\(=\dfrac{x+1-4x}{2\left(x-1\right)}\)
\(=\dfrac{1-3x}{2\left(x-1\right)}\)
c) \(\dfrac{y-12}{6y-36}+\dfrac{6}{y^2-6y}\)
\(=\dfrac{y-12}{6\left(y-6\right)}+\dfrac{6}{y\left(y-6\right)}\) MTC: \(6y\left(y-6\right)\)
\(=\dfrac{y\left(y-12\right)}{6y\left(y-6\right)}+\dfrac{6.6}{6y\left(y-6\right)}\)
\(=\dfrac{y\left(y-12\right)+6^2}{6y\left(y-6\right)}\)
\(=\dfrac{y^2-12y+6^2}{6y\left(y-6\right)}\)
\(=\dfrac{\left(y-6\right)^2}{6y\left(y-6\right)}\)
\(=\dfrac{y-6}{6y}\)
27 tháng 11 2017
Bạn Nguyễn Nam làm sai câu b rồi , làm lại cho tất nè
a) \(\dfrac{2}{x+3}+\dfrac{1}{x}=\dfrac{2x+x+3}{x\left(x+3\right)}=\dfrac{3x+3}{x\left(x+3\right)}\)
b) \(\dfrac{x+1}{2x-2}+\dfrac{-2x}{x^2-1}=\dfrac{x+1}{2\left(x-1\right)}-\dfrac{2x}{\left(x-1\right)\left(x+1\right)}\)
\(=\dfrac{\left(x+1\right)^2-4x}{2\left(x-1\right)\left(x+1\right)}=\dfrac{x^2+2x+1-4x}{2\left(x-1\right)\left(x+1\right)}=\dfrac{x^2-2x+1}{2\left(x-1\right)\left(x+1\right)}\)
\(=\dfrac{\left(x-1\right)^2}{2\left(x-1\right)\left(x+1\right)}=\dfrac{x-1}{2\left(x+1\right)}\)
c) \(\dfrac{y-12}{6y-36}+\dfrac{6}{y^2-6y}=\dfrac{y-12}{6\left(y-6\right)}+\dfrac{6}{y\left(y-6\right)}\)
\(=\dfrac{y^2-12y+36}{6y\left(y-6\right)}=\dfrac{\left(y-6\right)^2}{6y\left(y-6\right)}=\dfrac{y-6}{6y}\)
d) \(\dfrac{6x}{x+3}+\dfrac{3}{2x+6}=\dfrac{6x}{x+3}+\dfrac{3}{2\left(x+3\right)}=\dfrac{12x}{2\left(x+3\right)}\)( sửa đề )