Chưng minh rằng :
\(\frac{1.2-1}{2\text{!}}+\frac{2.3-1}{3\text{!}}+\frac{3.\text{4}-1}{\text{4}\text{!}}+...+\frac{99.100-1}{100\text{!}}< 2\)
Cho \(\frac{x^{\text{4}}}{a}+\frac{y^{\text{4}}}{b}=\frac{1}{a+b};x^2+y^2=1\)
Chứng minh rằng:\(\frac{x^{200\text{4}}}{a^{1002}}+\frac{y^{200\text{4}}}{b^{1002}}=\frac{2}{\left(a+b\right)^{102}}\)
( Câu siêu khó dành cho học sinh đội tuyển Toán )
( Giúp với )
Bài 10 :
b) \(\frac{\left(\text{13}\frac{\text{1}}{\text{4}}-\text{2}\frac{\text{5}}{\text{27}}-\text{10}\frac{\text{5}}{\text{6}}\right).\text{230}\frac{\text{1}}{\text{25}}+\text{46}\frac{\text{3}}{\text{4}}}{\left(\text{1}\frac{\text{3}}{\text{7}}+\frac{\text{10}}{\text{3}}\right):\left(\text{12}\frac{\text{1}}{\text{3}}-\text{14}\frac{\text{2}}{\text{7}}\right)}\)
Chứng minh rằng:
\(\frac{1}{2!}+\frac{2}{3!}+\frac{3}{4!}+...+\frac{n-1}{n!}< 1\text{ }\)
CMR:
\(\frac{1}{1.2.3}+\frac{1}{2.3.\text{4}}+\frac{1}{3.\text{4}.5}+...+\frac{1}{98.99.100}=\frac{\text{4}9\text{4}9}{19800}\)
\(\frac{\text{1}}{5x8}\) + \(\frac{\text{1}}{8x\text{1}\text{1}}\)+ \(\frac{\text{1}}{\text{1}\text{1}x\text{1}4}\) + ..... + \(\frac{\text{1}}{x\left(x+3\right)}\)= \(\frac{\text{1}0\text{1}}{\text{1}540}\)
4.\(\left(\frac{1}{4}\right)^2+25.\text{[}\text{ }\left(\frac{3}{4}\right)^3:\left(\frac{5}{4}\right)^3\text{]}:\left(\frac{3}{2}\right)^3\)
Tìm \(\text{n}\inℕ\), biết :
\(\frac{1}{\sqrt{1}+\sqrt{2}}+\frac{1}{\sqrt{2}+\sqrt{3}}+\frac{1}{\sqrt{3}+\sqrt{4}}+...+\frac{1}{\sqrt{\text{n}-1}+\sqrt{\text{n}}}=11\).
Cho C=\(\text{}\text{}\frac{a}{b+c}+\frac{b}{a+c}+\frac{c}{a+b}\left(a>0,b>0,c>0\right)\)và D=\(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{2017^2}\)
Chứng minh C>D