1/8+1/24+1/48+1/80+1/120+1/168+1/224
=1/(2×4)+1/(4×6)+1/(6×8)+1/(8×10)+1/(10×12)+1/(12×14)+1/(14×16)
=1/2(1/2-1/4+1/4-1/6+.+1/14-1/16)
=1/2(1/2-1/16)
=7/32
1/8+1/24+1/48+1/80+1/120+1/168+1/224
=1/(2×4)+1/(4×6)+1/(6×8)+1/(8×10)+1/(10×12)+1/(12×14)+1/(14×16)
=1/2(1/2-1/4+1/4-1/6+.+1/14-1/16)
=1/2(1/2-1/16)
=7/32