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=//__9.6__//= Objectives Develop and use the equations of a circle Adjust the equation for a circle to move the center in a coordinate plane

There is two generic equations that you can have when you are doing equations for circles... x square + y squared = r squared or (x+h)squared+(y+k)squared=r squared

when you have the first equation your center will be a (0,0) the origin of the graph when you have the second equation you will take the h and the k values and find the oppisite to get the origin...like this you have the equation (x+7)squared+(y-3)squared=r squared your center point would be at (-7,3) because you want the oppisites the r in the equation is the radius of the circle

So here are some problems to try: you have this question:Find the x- and y- intercepts for the graph of each equation and the give you this equation x squared + y squared = 49 first you should find the center and the radius as i said before when you have just x and ys your center will always be (0,0) and to find the radius you just take the sqare root of the number right of the = sign in this case it would be 49 and the square root of the is 7 so your center is (0,0) and your radius is 7 so your graph would look something like this...and the x intercepts would be (7,0) and (-7,0) the y intercepts are (0,7) and (0,-7) This is another question that could be asked it...Find the center and the radius of each circle...we just did this up above you have a equation like this (x-6)squared+(y+1)squared=81 to get the center you just take the oppisites of the h,k values so the center is (6,-1) and to get the radius you just take the squared root of the number right of the = sign square root of 81 = 9 so your radius would be 9 so your answer would be center=(6,-1) and radius=9

finally you could be asked this..Write an equation for the circle with the given center and radius Center: (-1,-8); radius= 4 first you would find the center which is the oppisite of the number above so your beginning of the equation would look like this (x+1)squared + (y+8) = and the second part of the equation would just be 4 squared (x+1)squared+(y+8)squared=16

DONE!!!