Answer
$-(3x-1)^{2}$
Work Step by Step
Expression : $-9x^{2}+6x-1 = -(9x^{2}-6x+1)$
By the well known formula $(a-b)^{2} = a^{2} -2ab +b^{2}$
$(9x^{2}-6x+1) = (3x)^{2}-2(3x)(1)+1^{2} = (3x-1)^{2}$
Hence, $-9x^{2}+6x-1 = -(9x^{2}-6x+1) = -(3x-1)^{2}$
