Tính nhanh
1) 9 x 10 + 10 x 11 + 11 x 12 + ....+ 2015 x 2016
2) 1 x 2 x 3 + 2 x 3 x 4 + 3 x 4 x 5 + ....+ 2015 x 2016 x 2017
\(A=\left(6:\frac{3}{5}-1\frac{1}{6}x\frac{6}{7}\right):\left(4\frac{1}{5}x\frac{10}{11}+5\frac{2}{11}\right)\)\(B=\left(1-\frac{1}{2}\right)x\left(1-\frac{1}{4}\right)x.......x\left(1-\frac{1}{2015}\right)x\left(1-\frac{1}{2016}\right)\)
\(C=5\frac{9}{10}:\frac{3}{2}-\left(2\frac{1}{3}x4\frac{1}{2}-2x2\frac{1}{3}\right):\frac{7}{4}\)
(1-1/2)x(1-1/3)x(1-1/4)x...x(1-1/2015)x(1-1/2016)
tính giá trị biểu thứ
A = (6:3/5 -1/1/6 x 6/7 ) : (4/1/5 x10/11+5/2/11)
B = (1-1/2)(1-1/3)(1-1/4)...(1-1/2016)(1-1/2017)
Tính (1-1/2)x(1-1/3)x(1-1/4)x( 1-1/5)x .........( 1-1/2015)x(1-1/2016)
A = (1 - 1/2) x (1 - 1/3) x (1 - 1/4) x (1 - 1/5) x ... (1 - 1/2016) x (1 - 1/2017)
(1-1/2) x (1-1/3) x (1 -1/4) x.....x (1-1/2014) x ((1-1/2015) x (1-1/2016)
A=(1-1/2)x(1-1/3)x(1-1/4)...(1-1/2016)x(1-1/2017)
Tính nhanh
c) C=(1 – 1/2) x ( 1 - 1/3) x (1 – 1/4) x (1 – 1/5) x (1 – 1/6) x ……….. x ( 1 - 1/2015 ) x ( 1- 1/2016)