Answer
$(3x-1)^2$
Work Step by Step
RECALL:
A perfect square trinomial can be factored using either of the following formulas.
(i) $a^2+2ab+b^2=(a+b)^2.$
(i) $a^2-2ab+b^2=(a-b)^2.$
The given perfect square trinomial can be written as
$(3x)^2-2(3x)(1)+1^2.$
Factor using formula (ii) above with $a=3x$ and $b=1$ to obtain
$(3x-1)^2.$