Find the center and radius of the circle x2 + y2 – 16x = 0

The answer is (8)
Move all variables to the left side and all constants to the right side.x2+y2−16x=0

Complete the square for x2−16x
(x−8)2−64

Substitute (x-8)2-64 for x2−16x in the equation       
 
x2+y2−16x=0x2+y2-16x=0 - (x−8)2−64+y2=0

Move −64 to the right side of the equation by adding 64 to both sides.
(x−8)2+y2=0+64

Add 0 and 64 to get 64.
(x-8)2+y2=64

This is the form of a circle. Use this form to determine the center and radius of the circle.
(x−h)2+(y−k)2=r2

Match the values in this circle to those of the standard form. The variable r represents the radius of the circle, h represents the x-offset from the origin, and k represents the y-offset from origin.
r=8h=8k=0

The center of the circle is found at (h,k).Center: (8,0)

These values represent the important values for graphing and analyzing a circle.Center: (8,0)Radius: 8

For the first question the answer is a, for the second c, for the third d, for the 4th b, for the 5th a