#y=(x-3)^2-4x^2-x+4#
#"1-take derivative of the function with respect to x"#
#(d y)/(d x)=2(x-3)*1-8x-1#
#"1-equalize with zero and solve for x"#
#2(x-3)-8x-1=0#
#2x-6-8x-1=0#
#-6x-7=0#
#-6x=7#
#x=-6/7#
#"write x=-6/7 in the original equation and calculate for y"#
#y=(-6/7-3)^2-4(-6/7)^2-(-6/7)+4#
#y=(-27/7)^2-4(36/49)+6/7+4#
#y=729/49-144/49+34/7#
#y=585/49+34/7#
#y=585/49+238/49#
#y=823/49#
#y=16.8#