2/1*2+2/2*3+2/3*4+2/4*5+2/5*6+2/6*7+2/7*8

2*(1/1*2+1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8) 1/1*2+1/2*3=(1*3+1)/1*2*3=4/2*3=2/3 2/3+1/3*4=(2*4+1)/3*4=9/3*4=3/4 3/4+1/4*5=(3*5+1)/4*5=16/4*5=4/5 4/5+1/5*6=(4*6+1)/5*6=25/5*6=5/6 5/6+1/6*7=(5*7+1)/6*7=36/6*7=6/7 6/7+1/7*8=(6*8+1)/7*8=49/7*8=7/8 2*(7/8)=7/4=1.25