Thread: arghh!!! please help - new to this hope im posting correctly

Originally Posted by loes

Points A (3,1), B(-1,-11), C(-5,9)

what the slope that passes through A and B

Plug the two points into slope formula.

Originally Posted by loes

whats the co-ordinates of the midpoint of the line segment AB

Plug the two points into the Midpoint Formula.

Originally Posted by loes

whats the equation of the perpendicular bisector of AB

How are perpendicular slopes related? Use this relationship to use the slope found above to find the perpendicular slope.

Then use the midpoint and this slope to find equation of the bisector. It would probably be simplest to start with the point-slope formula.

Originally Posted by loes

?? show that the line corresponding to the parametric equations

x = t - 14
y = -1/3t
is the same as the perpendicular bisector of AB

Solve the first equation for "t=", and plug this into the second equation. Simplify, and compare.

Originally Posted by loes

what is the equation of the perpendicular bisector of the line segment AC

Follow the same procedure as above: find the midpoint, find the slope, find the perpendicular slope, and then find the line equation.

Originally Posted by loes

from the answers of the above find the centre of the circle that passes through a b c

The two line equations form a system of equations. Solve the system to find the intersection point, and thus the center.

Originally Posted by loes

whats the radius of this circle

Plug the center and any of the three given points on the circle into the Distance Formula.

Originally Posted by loes

what the equation of this circle

Plug the center (h, k) and the radius r into the center equation (x - h)^2 + (y - k)^2 = r^2.

If you get stuck, please reply showing how far you have gotten. Thank you!