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show that the points (4,0), (2,1), (-1,-5) are the vertices of a right triangle and find its area.
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This is your triangle.
Calculate the distances between the given points (4,0), (2,1), (-1,-5).
1. Points (4,0) and (2,1). The distance a = = = .
2. Points (2,1) and (-1,-5). The distance b = = = = .
3. Points (4,0) and (-1,-5). The distance c = = = = .
Now you see that + = 5 + 45 = 50 = .
It is just enough to conclude that the triangle is right-angled.
Next, the area of the triangle is = = = = 7.5 .