If a and b be positive integers such that a2 – b2= 19,

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If a and b be positive integers such that a² – b²= 19, then the value of a is

1. 19
2. 20
3. 9
4. 10

Correct Option: D

Tricky approach
a² – b² = 19
⇒ 10² – 9² = 19
⇒ a = 10