Question

（1/3-7/12+9/20-11/30+13/42-15/56)x2^3x21

Answer 1

（1/3-7/12+9/20-11/30+13/42-15/56)x2^3x21

=[1/3-(1/3+1/1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)]x2^3x21

=(-1/8)x2^3x21

=-21