вычислить сумму 1\4+1\28+1\70+… +1\2011*2014
1\4+1\28+1\70+… +1\2011*2014 = = 1/3 * (3/4+3/28+3/70+...+3/(2011*2014))= = 1/3 * (3/(1*4)+3/(4*7)+3/(7*10)+...+3/(2011*2014))= = 1/3* (1/1-1/4+1/4-1/7+1/7-1/10+...+1/2001-1/2014) = = 1/3* (1-1/2014) = 1/3 * 2013/2014 = 671/2014