We need to do the following substitutions into the expression:
#color(red)(6)# for #color(red)(w)#
#color(blue)(0.4)# for #color(blue)(x)#
#color(green)(1/2)# for #color(green)(y)#
#color(purple)(-3)# for #color(purple)(z)#
#(color(blue)(x) - color(green)(y))^2 - 2color(red)(w)color(purple)(z)# becomes:
#(color(blue)(0.4) - color(green)(1/2))^2 - (2 * color(red)(6) * color(purple)(-3)) =>#
#(color(blue)(0.4) - color(green)(0.5))^2 - (12 * color(purple)(-3)) =>#
#(-0.1)^2 - (-36) =>#
#0.01 + 36 =>#
#36.01#