#### Answer

$(2t-7)^2$

#### Work Step by Step

The first term is $2t$ squared, the last term is $7$ squared, and the middle term is twice the negative product of these two terms. Now we can factor the trinomial into a binomial squared.
$4t^2-28t+49$
$=(2t-7)(2t-7)$
$=(2t-7)^2$