Tìm \(x_1\),\(x_2\),...\(x_{100}\) biết:
\(\frac{x_1-1}{100}\)=\(\frac{x_2-2}{99}\)=...=\(\frac{x_{100}-100}{1}\)
và \(x_1\)+\(x_2\) +...+\(x_{100}\)=15150
Tìm \(x_1,x_2,...,x_{100}\) thỏa mãn
\(\sqrt{x_1^2-1^2}+2\sqrt{x_2^2-2^2}+...+100\sqrt{x_{100}^2-100^2}=\dfrac{1}{2}\left(x_1^2+x_2^2+...+x_{100}^2\right)\)
\(\sqrt{x_1^2-1^2}+2\sqrt{x^2_2-2^2}+...+100\sqrt{x_{100}^2-100^2}=\dfrac{1}{2}\left(x_1^2+x^2_2+...+x_{100}^2\right)\)
\(\Leftrightarrow2\sqrt{x_1^2-1^2}+4\sqrt{x^2_2-2^2}+...+200\sqrt{x_{100}^2-100^2}=x_1^2+x^2_2+...+x_{100}^2\)
\(\Leftrightarrow x_1^2-1-2\sqrt{x_1^2-1}+1+x^2_2-4-4\sqrt{x^2_2-4}+4+...+x^2_{100}-10000-200\sqrt{x_{100}^2-10000}+10000=0\)
\(\Leftrightarrow\left(\sqrt{x^2_1-1}-1\right)^2+\left(\sqrt{x^2_2-4}-2\right)^2+....+\left(\sqrt{x^2_{100}-10000}-100\right)^2=0\)
\(\Rightarrow\left\{{}\begin{matrix}\sqrt{x^2_1-1}-1=0\\\sqrt{x^2_2-4}-2=0\\....\\\sqrt{x^2_{100}-10000}-100=0\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x_1=\sqrt{1^2+1}=\sqrt{2}\\x_2=\sqrt{2^2+4}=2\sqrt{2}\\....\\x_{100}=\sqrt{100^2+10000}=100\sqrt{2}\end{matrix}\right.\)
Bài 1 :
\(a,\)Tìm ƯCLN của số 11111111 và 111.....11111(có 1994 số 1)
\(b,\)Cho \(x_1+x_2+x_3+...+x_{100}+x_{101}=0\)
và \(x_1+x_2=x_3+x_4=...=x_{99}+x_{100}=x_{100}+x_{101}=1\)
tính \(x_{100}\)?
c, Tìm số nguyên tố ab(a>b>0), sao cho ab-ba là số chính phương.
Bài 2 :
a, so sánh
\(A=\frac{2009^{2008}+1}{2009^{2009}+1}\)
\(B=\frac{2009^{2009}+1}{2009^{2010}+1}\)
b, C=\(1\cdot3\cdot5\cdot7\cdot...\cdot99\)với D=\(\frac{51}{2}\cdot\frac{52}{2}\cdot\frac{53}{2}\cdot...\cdot\frac{100}{2}\)
mình cần lời giải chi tiết . ai giúp mình mình sẽ tick cho
tìm \(x_1;x_2;x_3;......;x_{2011}\) biet
\(\frac{x_1-1}{2010}=\frac{x_2-2}{2009}=.....=\frac{x_{2010}-2010}{1}\)va \(x_1+x_2+.....+x_{2011}=2\left(1+2+3+...+2010\right)\)
cho \(\frac{_{x_1}}{x_2}=\frac{x_2}{x_3}=\frac{x_3}{x_4}=\frac{x_4}{x_5}=...=\frac{x_{2008}}{x_{2009}}\). Chứng minh rằng: \(\left(\frac{x_1+x_2+x_3+x_4+...+x_{2008}}{x_2+x_3+x_4+x_5+...+x_{2009}}\right)^{2008}\) = \(\frac{x_1}{x_{2009}}\)
tìm \(x_1;x_2;x_3;......;x_{2011}\) biet
\(\frac{x_1-1}{2010}=\frac{x_2-2}{2009}=.....=\frac{x_{2010}-2010}{1}\)va \(x_1+x_2+.....+x_{2011}=2\left(1+2+3+...+2010\right)\)
\(\frac{x_1-1}{2010}=...=\frac{x_{2010}-2010}{1}=\frac{x_1+x_2+...+x_{2010}-\left(1+2+...+2010\right)}{2010+2009+...+1}\)
\(=\frac{2\left(1+2+...+2010\right)-\left(1+2+...+2010\right)}{1+2+...+2010}=1\)
Vậy thay vào ta được: \(x_1=x_2=...=x_{2010}=2011\)
tìm \(x_1;x_2;x_3;......;x_{2011}\) biet
\(\frac{x_1-1}{2010}=\frac{x_2-2}{2009}=.....=\frac{x_{2010}-2010}{1}\)va \(x_1+x_2+.....+x_{2011}=2\left(1+2+3+...+2010\right)\)
\(\frac{x_1-1}{2010}=\frac{x_2-2}{2009}=...=\frac{x_{2010}-2010}{1}=\frac{\left(x_1-1\right)+\left(x_2-2\right)+...+\left(x_{2010}-2010\right)}{1+2+...+2010}\) (TC DTSBN)
\(=\frac{\left(x_1+x_2+...+x_{2010}\right)-\left(1+2+...+2010\right)}{1+2+...+2010}=\frac{2.\left(1+2+...+2010\right)-\left(1+2+...+2010\right)}{1+2+...+2010}=1\)
\(\Rightarrow x_1-1=2010;x_2-1=2009;....;x_{2010}-2010=1\)
=> x1 = x2 = x3 =..... = x2010 = 2011
tìm \(x_1,x_2,x_3.......,x_9\)
\(\frac{x_{1-1}}{9}=\frac{x_{2-2}}{8}=\frac{x_3-3}{7}=....=\frac{x_{9-9}}{1}\) và \(x_1+x_2+x_3+...+x_9=90\)
Cho:
\(\frac{x_1-1}{2017}=\frac{x_2-2}{2016}=\frac{x_3-3}{2015}=...=\frac{x_{2017}-2017}{1}vàx_1+x_2+...+x_{2017=2017\cdot2018.}Tìmx_1,x_2,x_{3,...,x_{2017}?}\)
\(\frac{x_1-1}{2010}=\frac{x_2-2}{2009}=.....=\frac{x_{2010}-2010}{1}\)va \(x_1+x_2+x_3+...+x_{2011}=2\left(1+2+3+...+2011\right)\)