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deerhunter15
 one year ago
The equation below represents a circle.
x2 + y2 + 4x – 2y = a
Part A: What is the x coordinate of the center of the circle?
Part B: What is the y coordinate of the center of the circle?
Part C: What is the value of a in the equation if the radius of the circle is 8?
deerhunter15
 one year ago
The equation below represents a circle. x2 + y2 + 4x – 2y = a Part A: What is the x coordinate of the center of the circle? Part B: What is the y coordinate of the center of the circle? Part C: What is the value of a in the equation if the radius of the circle is 8?

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welshfella
 one year ago
Best ResponseYou've already chosen the best response.1do you know how to complete the square?

deerhunter15
 one year ago
Best ResponseYou've already chosen the best response.0no @welshfella I've never learned this stuff :/

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1x^2 + 4x = (x + 2)^2  4 you divide the coefficient of x by 2  in this case its 4/2 = 2 so this gives(x + 2) ^2 when you expand that you get +4 so you have to subtract 4 so that its = to x^2 + 4x.

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1we intend to convert the equation of the circle to the standard form (x  a)^2 + (y  b)^2 = r^2 here (a,b) is the center of circle and r = radius

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1so comparing (x  a) and ( x + 2) we see that a = + 2 give a = 2 so 2 is the x coordinate of the center of circle

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1now you can work out the y coordinate in a sismilar way by completing the square on y^2  2y

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1I'll start you off; y^2  2y divide 2 by 2 = 1 so we have (x  1)^2  A what will A be?

deerhunter15
 one year ago
Best ResponseYou've already chosen the best response.01x^2=A @welshfella

welshfella
 one year ago
Best ResponseYou've already chosen the best response.1no A willo be 1 because (x  1)^2 = x^2  2x + 1 so to get this back to x^2  2x we have to subtract 1

deerhunter15
 one year ago
Best ResponseYou've already chosen the best response.0@welshfella whats y?
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