Two positive integers differ by 4, and sum of their reciprocals is 1. Then one of the numbers is  Select:
A) 2
B) b) 1
C) c) 5
D) d) 21
E) e) 28
Algebraic approach:   Let n be the smaller integer =&gt; 1/n + 1/(n+4) = 1 or ((n+4)+n)/n(n+4) =1 or n^2+4n =2n+4 or n=2 as n cannot be -negative   Solve for n =&gt; n=2. Hence,   2
<result>A</result>
Two positive integers differ by 4, and sum of their reciprocals is 1. Then one of the numbers is