Question

The general form of the equation of a circle is Ax2 By2 Cx Dy E = 0, where A = B 0. If the circle has a radius of 3 units and the center at (0, 4), which set of values of A, B, C, D, and E correspond to the circle?

Answer 1

Answer:

PLATO SAMPLE ANSWER:

If the center of the circle is to the right of the y-axis, C is negative and its absolute value increases as the center moves to the right. If the center is to the left of the y-axis, C is positive and its value decreases as the center moves to the right. D does not change when the center moves horizontally.

If the center of the circle is above the x-axis, D is negative and its absolute value increases as the center moves up. If the center is below the y-axis, D is positive and its value decreases as the center moves up. C does not change when the center moves vertically.

The values of C and D are not affected when the radius changes, as long as the center stays the same.

Answer 2

The other form of circle equation is (x-a)2 + (y-b)2 = r2. a and b is the coordinate of the center and r is radius. So the equation is x2+(y-4)2=9. Change it to the general form is x2+y2-8y+7=0. So A=1, B=1, C=0, D=-8 and E=7.