Question

chứng minh rằng : S=6/2.5 + 6/5.8 + .... +  6/26.29 + 6/29/32 < 1

Answer 1

S=6/2*5+6/5*8+...+6/29*32

=6/3*(3/2*5+3/5*8+...+3/29*32)

=2*(1/2-1/5+1/5-1/8+...+1/29-1/32)

=2*(1/2-1/32)=2*15/32

=15/16<1

Answer 2

S=6/2*5+6/5*8+...+6/29*32,c

=6/3*(3/2*5+3/5*8+...+3/29*32)

=2*(1/2-1/5+1/5-1/8+...+1/29-1/32)

=2*(1/2-1/32)

=2*15/32

=15/16<1