The general vertex form for a quadratic is #y = m(x-a)+b# where #(a,b)# is the vertex.
#y=2x^2-12x+11# #color(white)("XXXX")#extract the #m# #y=2(x^2-6x) +11# #color(white)("XXXX")#complete the square #y=2(x^2-6x+9) +11 -18# #color(white)("XXXX")#simplify to vertex form #y=2(x-3)^2 + (-7)# #color(white)("XXXX")#with the vertex at #(3,-7)#