1/10*12+1/12*14+1/14*16+1/16*18有没有看懂.

Question

1/10*12+1/12*14+1/14*16+1/16*18
有没有看懂.

Answer 1

1/10*12+1/12*14+1/14*16+1/16*18
=(1/10-1/12)/2+(1/12-1/14)/2+(1/14-1/16)/2+(1/16-1/18)/2
=(1/10-1/18)/2
=4/180
=1/45