How do you find the coordinates of the center of the circle #x^2 +y^2 -4x+ 6x =12#? Precalculus Geometry of an Ellipse Standard Form of the Equation 1 Answer ali ergin Mar 11, 2016 #r=7/2# Explanation: #x^2+y^2-4x+6x=12# #x^2+y^2+2x-12=0# #x^2+y^2+D x+E y+F=0# #C(a,b) " center coordinates"# #D=2" "E=0" "F=-12# #a=-D/2=-2/2=-1# #b=-E/2=0/2=0# #r=1/2*sqrt(D^2+E^2-4*F)# #r=1/2*sqrt((-1)^2+0+4*12)# #r=1/2*sqrt(1+48)# #r=1/2*sqrt 49# #r=7/2# Answer link Related questions What is meant by an ellipse in standard form? What are common mistakes students make with ellipses in standard form? How do I write an ellipse in standard form? How do I find the center of an ellipse in standard form? What is the major axis of an ellipse? How do I find the major and minor axes of an ellipse? How do I know whether the major axis of an ellipse is horizontal or vertical? How do I find the center of an ellipse with the equation #9x^2+16y^2-18x+64y=71#? How do I use completing the square to rewrite the equation of an ellipse in standard form? What do #a# and #b# represent in the standard form of the equation for an ellipse? See all questions in Standard Form of the Equation Impact of this question 1204 views around the world You can reuse this answer Creative Commons License