Plot the points on a graph. Connect the dots into a triangle. See that the height of the triangle is from y=5 down to y=1. So the height is 4 units.
Area of a triangle: A = (1/2)BH
You need to find the length of the base. Which is from point (-4,1) to (0,1). You can use the distance formula r just see from the graph that the base is 4 units.
A = (1/2)(4)(4)
A = 8
** Distance formula fyi
d² = (X-x)² + (Y-y)²
with points (X,Y) and (x,y)