5/9*2/17+4/17*2/9
=5/9*2/17+2/17*4/9
=2/17*(5/9+4/9)
=2/17
3/4+3/28+3/70+3/130+3/208
=3/1*4+3/4*7+3/7*10+3/10*13+3/13*16
=3/3*(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+1/13-1/16)
=1-1/16
=15/16
5/9*2/17+4/17*2/9
=5/9*2/17+2/17*4/9
=2/17*(5/9+4/9)
=2/17
3/4+3/28+3/70+3/130+3/208
=3/1*4+3/4*7+3/7*10+3/10*13+3/13*16
=3/3*(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13+1/13-1/16)
=1-1/16
=15/16