What is the standard form of this equation of #x^ { 2} + y ^ { 2} + 14x - 4y - 28= 0#?

1 Answer
Aug 17, 2017

#(x+7)^2+(y-2)^2=81#

Explanation:

#"using the method of "color(blue)"completing the square"#

#"collect the x and y terms together"#

#x^2+14x+y^2-4y=28#

#rArr(x+7)^2+(y-2)^2=28color(red)(+49+4)#

#rArr(x+7)^2+(y-2)^2=81larr" in standard form"#

#"this is the equation of a circle with"#

#"centre "=(-7,2)" and radius "=9#
graph{((x+7)^2+(y-2)^2-81)=0 [-40, 40, -20, 20]}