We can use this rule for quadratics to expand this expression:
#(color(red)(a) + color(blue)(b))^2 = (color(red)(a) + color(blue)(b))(color(red)(a) + color(blue)(b)) = color(red)(a)^2 + 2color(red)(a)color(blue)(b) + color(blue)(b)^2#
Let: #color(red)(a) = color(red)(6xy)#
Let: #color(blue)(b) = color(blue)(8)#
Substitute and write the expression as:
#(color(red)(6xy) + color(blue)(8))^2 =>#
#(color(red)(6xy) + color(blue)(8))(color(red)(6xy) + color(blue)(8)) =>#
#color(red)((6xy))^2 + (2 * color(red)(6xy) * color(blue)(8)) + color(blue)(8)^2 =>#
#36x^2y^2 + 96xy + 64#