tinh \(M=\left(\frac{1}{2^2}-1\right).\left(\frac{1}{3^2}-1\right).\left(\frac{1}{4^2}\right)....\left(\frac{1}{100^2}-1\right)< 0\)
1, Tính \(\frac{1}{2}-\left(\frac{1}{3}+\frac{2}{3}\right)+\left(\frac{1}{4}+\frac{2}{4}+\frac{3}{4}\right)-\left(\frac{1}{5}+\frac{2}{5}+\frac{3}{5}+\frac{4}{5}\right)+...+\left(\frac{1}{100}+\frac{2}{100}+\frac{3}{100}+...+\frac{99}{100}\right)\)2,Tính \(\left(1-\frac{1}{2^2}\right)x\left(1-\frac{1}{3^2}\right)x\left(1-\frac{1}{4^2}\right)x...x\left(1-\frac{1}{n^2}\right)\)
Tinh
\(\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)\left(1-\frac{1}{4}\right).......\left(1-\frac{1}{100}\right)+x=2+\frac{1}{5}\)
\(\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)\left(1-\frac{1}{4}\right)......\left(1-\frac{1}{100}\right)+x=2+\frac{1}{5}\)
\(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}......\frac{99}{100}+x=\frac{11}{5}\)
\(\frac{1}{100}+x=\frac{11}{5}\)
\(x=\frac{11}{5}-\frac{1}{100}=\frac{219}{100}\)
X=219/100 đó nha!
chúc may mắn!!!
Thuc hien phep tinh
e)\(\left(\frac{2}{3}-\frac{-2}{7}-\frac{1}{14}\right):\left(-1-\frac{3}{7}+\frac{3}{28}\right)\)
f) \(\left(\frac{1}{2}-1\right)\left(\frac{1}{3}-1\right)\cdot\left(\frac{1}{4}-1\right)...\left(\frac{1}{100}-1\right)\)
\(\frac{1}{x\left(x+1\right)}+\frac{1}{\left(x+1\right)\left(x+2\right)}+\frac{1}{\left(x+2\right)+\left(x+3\right)}+\frac{1}{\left(x+3\right)\left(x+4\right)}=\frac{m}{x\left(x+4\right)}\)
Tinh so m
\(VT=\frac{1}{x\left(x+1\right)}+\frac{1}{\left(x+1\right)\left(x+2\right)}+...+\frac{1}{\left(x+3\right)\left(x+4\right)}\)
\(=\frac{1}{x}-\frac{1}{x+1}+\frac{1}{x+1}-\frac{1}{x+2}+...+\frac{1}{x+3}-\frac{1}{x+4}\)
\(=\frac{1}{x}-\frac{1}{x+4}=\frac{x+4-x}{x\left(x+4\right)}=\frac{4}{x\left(x+4\right)}\)
\(\Rightarrow\frac{4}{x\left(x+4\right)}=\frac{m}{x\left(x+4\right)}=VP\Rightarrow m=4\)
Tự ý sửa đề; để làm theo ý mình là sao?
cái đề số hạng thứ 3 là dấu (+) không phải (.) nhé
viết lại pt dưới dạng thần thánh
\(x^2-\frac{2mx}{\left(m-1\right)}+\frac{\left(c+1\right)}{4\left(m-1\right)}=0.\)
\(\left(x^2-\frac{2mx}{\left(m-1\right)}+\frac{m^2}{\left(m-1\right)^2}\right)+\frac{\left(c+1\right)}{4\left(m-1\right)}-\frac{m^2}{\left(m-1\right)^2}=0\)
\(\left(x-\frac{m}{\left(m-1\right)}\right)^2=\frac{4m^2-\left(c+1\right)\left(m-1\right)}{4\left(m-1\right)^2}\)
vậy pt có 2 nghiệm phân biệt :
\(\Leftrightarrow\hept{\begin{cases}\left(x-\frac{m}{m-1}\right)=\sqrt{\frac{4m^2-\left(c+1\right)\left(m-1\right)}{4\left(m-1\right)^2}}\\\left(x-\frac{m}{m-1}\right)=-\sqrt{\frac{4m^2-\left(c+1\right)\left(m-1\right)}{4\left(m-1\right)^2}}\end{cases}}\) " sủa lên nào em
Thực hiện phép tính :
a, A =\(\left(1:\frac{5^2}{10^2}\right).\left(1\frac{1}{1}\right)^2+25.\left[1:\left(\frac{4}{3}\right)^2:\left(\frac{5}{4}\right)^3\right]:\left(1:\frac{-8}{27}\right)\)
b, B =\(\left(1-\frac{1}{2^2}\right).\left(1-\frac{1}{3^2}\right).\left(1-\frac{1}{4^2}\right)...\left(1-\frac{1}{100^2}\right)\)
a) \(A=\left(1:\frac{1}{4}\right).4+25\left(1:\frac{16}{9}:\frac{125}{64}\right):\left(-\frac{27}{8}\right)\)
\(=4.4+25.\frac{36}{125}:\frac{-27}{8}\)
\(=16-\frac{32}{15}=\frac{240}{15}-\frac{32}{15}=\frac{208}{15}\)
tinh
\(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right).....\left(1-\frac{1}{100}\right)\)
\(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right)...\left(1-\frac{1}{100}\right)\)
=\(\frac{1}{2}.\frac{2}{3}.\frac{3}{4}...\frac{99}{100}\)
=\(\frac{1.2.3...99}{2.3.4...100}\)
=\(\frac{1}{100}\)
Chúc bạn học giỏi nha
\(=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot...\cdot\frac{99}{100}\)
\(=\frac{1\cdot2\cdot3\cdot4\cdot...\cdot99}{2\cdot3\cdot4\cdot5\cdot...\cdot100}\)
\(=\frac{1}{100}\)
Tính :
\(\left[\frac{1}{100}-1^2\right].\left[\frac{1}{100}-\left(\frac{1}{2}\right)^2\right].\left[\frac{1}{100}-\left(\frac{1}{3}\right)^2\right]...\left[\frac{1}{100}-\left(\frac{1}{20}\right)^2\right]\)
Tính:
\(\left[\frac{1}{100}-1^2\right].\left[\frac{1}{100}-\left(\frac{1}{2}\right)^2\right].\left[\frac{1}{100}-\left(\frac{1}{3}\right)^2\right].....\left[\frac{1}{100}-\left(\frac{1}{20}\right)^2\right]\)
Xét : \(\frac{1}{100}-\frac{1}{n^2}=\frac{n^2-100}{100n^2}=\frac{\left(n-10\right)\left(n+10\right)}{100n^2}\)
Áp dụng , đặt biểu thức cần tính là A , ta có :
\(A=\left(\frac{1}{100}-\frac{1}{1^2}\right)\left(\frac{1}{100}-\frac{1}{2^2}\right)\left(\frac{1}{100}-\frac{1}{3^2}\right)...\left(\frac{1}{100}-\frac{1}{20^2}\right)\)
\(=\frac{\left(1-10\right)\left(1+10\right)}{100.1^2}.\frac{\left(2-10\right)\left(2+10\right)}{100.2^2}.\frac{\left(3-10\right)\left(3+10\right)}{100.3^2}...\frac{\left(10-10\right)\left(10+10\right)}{100.10^2}...\frac{\left(20-10\right)\left(20+10\right)}{100.20^2}\)
Nhận thấy trong A có một nhân tử (10-10) = 0 nên A = 0
làm thế thì hơi dài đấy Hoàng Lê Bảo Ngọc
ta nhận thấy trong biểu thức chứa thừa số \(\frac{1}{100}-\left(\frac{1}{10}\right)^2=\frac{1}{100}-\frac{1}{100}=0\)
=>biểu thức ấy =0
Nguyễn Thiều Công Thành Ừ , tại mình quên không để ý :)