16k^2 + 16k + 4
We can first start off by dividing every term by 4:
4 (4k^2 + 4k + 1)
to factor, you find which two number you can multiply with each other to get the middle term. So 2 and 2 to get 4. Substitute that into the equation
4 (4k^2 + 2k + 2k + 1)
the first two terms become a group and the last 2 terms become a group. Factor like terms out of the two groups.
4 (2k (2k + 1) + 1 (2k + 1))
4 (2k + 1)(2k + 1)
