# Help please??

##### 1 Answer

Jun 2, 2018

We know that the surface area is the sum of the areas of all the surfaces. We start by seeing that the area of the square base is simply

The height of the triangles will be

#A_Delta= ((x(20 - x))/2)/2 * 4# (as there are 4 triangles)

#A_Delta = (x(20 - x))/4 * 4#

#A_Delta = # x(20 - x)#

#A_Delta = 20x - x^2#

Now simply add this to the area of the square

#A_"pyramid" = x^2 + 20x - x^2 = 20x#

As required.

Hopefully this helps!