Question

What is the equation of the following graph?　http://curriculum.kcdistancelearning.com/courses/ALG2x-HS-A09/b/assessments/C-CirclesQuiz/A2_8.3_Quiz_3q.gif


x2 + y2 = 4

x2 + y2 = 1

x2 + y2 = 16

x2 + y2 = 17

Answer 1

well, pick a point and see what fits, excepting that you forgot how to make a circle equation centered at the origin

Answer 2

I don't understand...
@amistre64

Answer 3

which part? picking a point, or seeing if it fits?

Answer 4

both... I have no idea how to do it.
@amistre64

Answer 5

hmm, well, we have a graph. the graph is defined by an x axis and a y axis. any point on the graph can be determine uniquely by it x part and y part such that the point (x,y) can be found.

the points that form a circle are marked by the circle that is drawn on the graph. choosing one of those points is the act of putting your finger or pencil or whatever you want to use to point to one of them, and then reading its (x,y) value.

Answer 6

now, to see if it fits one of the options, since we have an x and y value attributed to a point, it will have to make a true equation by replaceing the x variable with the x value of the point. and replacing the y variable with the y value of the point. then the adding operation and the equaling of it will either be true of false.

Answer 7

if its true, the equation is good, otherwise its not and we pick a different equation to test out

Answer 8

is it x2 + y2 = 16? @amistre64

Answer 9

if we choose the point: 0,4 then yes. 0^2 + 4^2 = 16 is a fine match.

Answer 10

thank you so much :)
@amistre64