( x 2 − 6 x + a ) − 1 2 ( − ( 2 x − 6 ) 2 4 ( x 2 − 6 x + a ) + 1 ) {\displaystyle \ (x^{2}-6x+a)^{-{\tfrac {1}{2}}}\left(-{\frac {(2x-6)^{2}}{4(x^{2}-6x+a)}}+1\right)}
