Question

1/1*5+1/5*9+1/9*13

Answer 1

1/1*5+1/5*9+1/9*13

=(1-1/5)/4+(1/5-1/9)/4+(1/9-1/13)/4

=[(1-1/5)+(1/5-1/9)+(1/9-1/13)]/4

=(1-1/13)/4

=3/13

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