Find the area of the shape shown below using the screenshot i took

For this case we have that the figure shown is composed of three triangles and a square. By definition, the area of a triangle is given by:

Where:

b: It's the base

h: It's the height

We have 3 triangles, then the sum of their areas will be:

On the other hand, the area of a square is given by:

Where:

l: It's the side of the square

According to the figure we have:

So, the total area is:

3x^3-x^2+6x-9