Okay,
so,
The given expression is :

As 16 is sqaure of 4 and 49 is square of 7, then this whole expression could also be written as

Now,
as you might've notices by now that this expression is in the form of

And there's an alzebric identity about it. That is

Now by using this alzebric identity. we're gonna split our expession as shown below:

By solving the last step i.e,
(11a-3b)(11b-3a)
we'll get,
121a^2 - 33ab -33b^2 -8ab
= 121a^2-33b^2 -41ab .