#### Answer

$(3t+7)(3t-7)$

#### Work Step by Step

$\bf{\text{Solution Outline:}}$
To factor the given expression, $
9t^2-49
,$ use the factoring of the difference of $2$ squares.
$\bf{\text{Solution Details:}}$
The expressions $
9t^2
$ and $
49
$ are both perfect squares (the square root is exact) and are separated by a minus sign. Hence, $
9t^2-49
,$ is a difference of $2$ squares. Using the factoring of the difference of $2$ squares which is given by $a^2-b^2=(a+b)(a-b),$ the expression above is equivalent to
\begin{array}{l}\require{cancel}
(3t)^2-(7)^2
\\\\=
(3t+7)(3t-7)
.\end{array}