Cho A = 1x2010+2x2009+3x2008+...+2010x1 và B = 1+( 1+2 ) +(1+2+3 ) +...+( 1+2+3+...+2010) . Tính A : B
Cho A = 1x2010+2x2009+3x2008+...+2010x1 và B = 1+( 1+2 ) +(1+2+3 ) +...+( 1+2+3+...+2010) . Tính A : B
Cho A = 1x2010+2x2009+3x2008+...+2010x1 và B = 1+( 1+2 ) +(1+2+3 ) +...+( 1+2+3+...+2010) . Tính A : B
Tính:
A = \(\frac{1+\left(1+2\right)+\left(1+2+3\right)+...+\left(1+2+3+...+99\right)}{1\times99+2\times98+3\times97+...+99\times1}\)
B = \(\frac{1\times2010+2\times2009+3\times2008+...+2010\times1}{\left(1+2+3+...+2010\right)+\left(1+2+3+...+2009\right)+...+\left(1+2\right)+1}\)
Tính nhanh: \(\left(2012\times2010+2010\times2008\right)\times\left(1+\dfrac{1}{2}\div1\dfrac{1}{2}-1\dfrac{1}{3}\right)\)
Tính bằng cách thuận tiện nhất:
\(\left(1-\dfrac{1}{2}\right)\text{× }\left(1-\dfrac{1}{3}\right)\text{ × }\left(1-\dfrac{1}{4}\right)\text{ × }\left(1-\dfrac{1}{5}\right)\text{}\text{}\text{× }\left(1-\dfrac{1}{6}\right)\)
Tính nhanh
B=\(\dfrac{1+\left(1+2\right)+\left(1+2+3\right)+.......+\left(1+2+......+2012\right)}{1}1x2012+2x2011+3x2010+....+2012x1\)
1. \(\left(y+\dfrac{1}{3}\right)\)+\(\left(y+\dfrac{1}{9}\right)\)+\(\left(y+\dfrac{1}{27}\right)\)+\(\left(y+\dfrac{1}{81}\right)\)=\(\dfrac{56}{81}\)
2. 18:\(\dfrac{Xx0,4+0,32}{X}\)+5=14
3. \(\dfrac{3xX}{2}\)=\(\dfrac{2}{5}+\)X\(+\dfrac{1}{3}\)
4. X-\(\dfrac{11}{15}\)=\(\dfrac{3+X}{5}\)
\(A=\dfrac{1+\left(1+2\right)+\left(1+2+3\right)+...+\left(1+2+3+...+2020\right)}{1\text{×}2020+2\text{×}2019+3\text{×}2018+...+2020\text{×}1}\)