Which of the following is a factor of (49x2−1)+(1+7x)2?
1+7x
(49x2−1)+(1+7x)2=(49x2−1)+(1+7x)(1+7x)
=(7x−1)(7x+1)+(1+7x)(1+7x)
[Since 49x2−1=(7x+1)(7x−1)]
=(1+7x)(7x−1+1+7x) [Taking (1+7x) as common]
=(1+7x)(14x)
Hence, (1+7x) is a factor of (49x2−1)+(1+7x)2.