Question

tính

B = 3/1x6 + 3/6x11 + ... + 1/91 x96

Answer 1

Sửa đề: 3/91*96

\(B=\dfrac{3}{1\cdot6}+\dfrac{3}{6\cdot11}+...+\dfrac{3}{91\cdot96}\)

=3/5(5/1*6+5/6*11+...+5/91*96)

=3/5(1-1/6+1/6-1/11+...+1/91-1/96)

=3/5*95/96=57/96=19/32