Các câu hỏi tương tự
7 tháng 12 2021 lúc 19:37
Tính:B=\(1+\dfrac{1}{2}\left(1+2\right)+\dfrac{1}{3}\left(1+2+3\right)+\dfrac{1}{4}\left(1+2+3+4\right)+...+\dfrac{1}{20}\left(1+2+3+...+20\right)\)
1+\(\dfrac{1}{2}\)(1+2)+\(\dfrac{1}{3}\left(1+2+3\right)\)+\(\dfrac{1}{4}\left(1+2+3+4\right)\)+...+\(\dfrac{1}{20}\left(1+2+3+...+20\right)\)
\(tínhhợplí:\left(1,2-\sqrt{\dfrac{1}{4}:1\dfrac{1}{20}+\left|-\dfrac{3}{4}\right|-\left(-\dfrac{3}{2}\right)^2}\right)\)
\(A=\left(1-\dfrac{1}{2}\right)\left(1-\dfrac{1}{3}\right)\left(1-\dfrac{1}{4}\right).....\left(1-\dfrac{1}{19}\right)\left(1-\dfrac{1}{20}\right)\)
So sinh A với \(\dfrac{1}{21}\)
Tính:
a/\(A=\left(-0,75-\dfrac{1}{4}\right):\left(-5\right)+\dfrac{1}{48}-\left(\dfrac{-1}{6}\right):\left(-3\right)\)
b/\(B=\left(\dfrac{6}{25}-1,24\right):\dfrac{3}{7}:\left[\left(3\dfrac{1}{2}-3\dfrac{2}{3}\right):\dfrac{1}{14}\right]\)
Tính
a) \(\dfrac{13}{50}.\left(-15.5\right):\dfrac{13}{50}.84\dfrac{1}{2}\)
b) \(\dfrac{\left(-0,7\right)^2.\left(-5\right)^3}{\left(-2\dfrac{1}{3}\right)^3.\left(1\dfrac{1}{2}\right)^4.\left(-1\right)^5}\)
Có mấy giá trị của x thỏa mãn bt dưới đây:
\(\dfrac{2}{\left(x-1\right)\left(x-3\right)}+\dfrac{5}{\left(x-3\right)\left(x-8\right)}+\dfrac{12}{\left(x-8\right)\left(x-20\right)}-\dfrac{1}{x-20}=\dfrac{-3}{4}\)
Tìm x biết:
a) \(2.\left|3x-1\right|-\dfrac{3}{4}=\dfrac{1}{20}\)
b) \(\left|x+5\right|+\left|x-3\right|=9\)
Tính:
a) (-0,4)2 - (-0,4)3 . (-3)
b) \(\left(1\dfrac{3}{4}\right)^3\) - \(\left(1\dfrac{3}{4}\right)^2\) + (-1,031)0
c) \(\left(\dfrac{2}{3}\right)^3\) - 4. \(\left(-1\dfrac{3}{4}\right)^2\) + \(\left(-\dfrac{2}{3}\right)^3\)