Question

What is the largest prime factor of $(30^2 -7^2)$?

Answer 1

37

Explanation:

From difference of squares, we have
`(a-b)(a+b)=a^2-b^2`. We can let a = 30 and b = 7 to have
`30^2-7^2=(30-7)(30+7)=(23)(37)` Since 37 and 23 are both prime, the largest prime factor is the biggest of the two, 37.