Answer:
(x+9)(x+9)
Explanation:
To factor this expression, we first need to put into standard form, that is,
.
So it becomes

Now we need to find two numbers that:
A. When multiplied get us c (81)
B. When added get us b (18)
9 and 9 match those requirements, so out product of two binomials for this becomes (x+9)(x+9).
Hope this helped!