You need to find the area of this
Step 1: Find the slope:
This gives you , but we need to find b.
To find b, substitute in one (x,y) pair and it doesn't matter which one. I'll go with (4,-2):
Now take that b-value and plug in into the slope-intercept form:
It's always a good idea to toss in the other x-value from the other point, to make sure it checks out.