Question

use words to explain how these formulas find the area of the parellelogram. 1/2ah + bh+ 1/2 ah

Answer 1

Factorize:
h(1/2a+b+1/2a)
=h(a+b)

You can't do this from here because a, b, h are all not defined.

Answer 2

The area of a triangle is its base times its height times 1/2. So, if a is the length of one of the little side-triangles' bases, then each 1/2ah represents one of the triangles sliced off of the parallelogram to leave a rectangle. The formula for area of a rectangle is bh, so that's where that came from.

Essentially: stick two equal (right) triangles onto a rectangle (with the right proportions in each of course) and you have a parallelogram.