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In such a case, the answers might help. Aren't there any choices? What is the source of the question?
The semi-perimeter s = 4 + 1.5sqrt(10)
The area is sqrt (6.5*13.75) using the formula sqrt[s(s-a)(s-b)(s-c)]
I am not sure if such complex calculations would be asked in the GMAT. Plotting the triangle helps to an extent. However with the given coordinates altitudes and bases are difficult to detemine.
I remember doing a question from the GMAT Prep test involving vertices, which flustered me. So I went looking for help. I found the example given in this thread on a math forum while looking for that help.
I found out how to solve the problem using 3x3 determinants but it is to confusing and hard to share at this moment. Perhaps I can show the technique using illustrator when I have time later this evening.
Yes, the answer is 8 and I got it by using a really simple technique:
what I did was just drawing a triangle and then inscribing it inside a rectangle with the vertices (-2;3)(3;3)(3;-4)(-2;-4). Now, it's pretty simple to find the area of the rectangle with sides 5 and 7, it's 35. Then I just substructed from this the 'extra' bits and pieces (three right triangles and a rectangle): 35-2-6-1.5-17.5=8