Check the picture below.
the box is an open box, meaning the top is open, so that is not taking up area, so is not part of the surface area.
so can just get the area of the bottom, and the sides and sum them up, keeping in mind that the bottom is just an area of x² and the sides are just 4 rectangles of area h*x.
the box is an open box, meaning the top is open, so that is not taking up area, so is not part of the surface area.
so can just get the area of the bottom, and the sides and sum them up, keeping in mind that the bottom is just an area of x² and the sides are just 4 rectangles of area h*x.