#1 is C
#2 is B
3a is On the circle
3b is inside
3d is on
3e is outside
4a is "You can find if a triangle is right by using the Pythagorean theorem or by using perpendicular lines"
4b): Using the Pythagorean Side AC (which is √10 units long)^2 + side AB (which is √40 units long)^2 is equal to 50 (which is the length of side BC). Using perpendicular lines, you find that line AB has a slope of 1/3 and side AC has a slope of -3. Since these two are opposite reciprocals, they are perpendicular, which means that they form a 90 degree angle.
5.) To find the midpoint, use the formula (x2+x1/2,y2+y1/2) by using the given coordinates, we find that the midpoint is (1,-2). This point lies in quadrant IV, so it is proven that it's midpoint lies in quadrant IV.
:)