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1) 9 x 10 + 10 x 11 + 11 x 12 + ....+ 2015 x 2016
=9x10x11-8x9x10+10x11x12-9x10x11+...+2015x2016x2017-2014x2015x2013
=2015x2016x2017-8x9x10
=8193537360
(1-1/2)x(1-1/3)x(1-1/4) x ...x (1-1/2016)
= 1/2x2/3x3/4x.....x2015/2016
= \(\frac{1x2x3x...x2015}{2x3x4x...x2016}\)
= 1/2016
\(\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times...\times\left(1-\frac{1}{2016}\right)\)
\(=\frac{1}{2}\times\frac{2}{3}\times...\times\frac{2015}{2016}\)
\(=\frac{1}{2016}\)
\(\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)..........\left(1-\frac{1}{2016}\right)\)
\(=\frac{1}{2}.\frac{2}{3}.........\frac{2015}{2016}\)
\(=\frac{1.2.......2015}{2.3.......2016}\)
\(=\frac{1}{2016}\)
\(\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)........\left(1-\frac{1}{2016}\right)\)
\(=\frac{1}{2}.\frac{2}{3}.......\frac{2015}{2016}=\frac{1}{2016}\)
\(A=\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times...\times\frac{2015}{2016}\times\frac{2016}{2017}=\frac{1}{2017}\)
A=(1-1/2)x(1-1/3)x.................x(1-1/2017)
A=\(\frac{1}{2}\times\frac{2}{3}\)x....x\(\frac{2016}{2017}\)
A=\(\frac{1}{2017}\)