How do you write the standard equation of a circle with the given radius and center: r=4; C(3,-4)?

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Answer 1 · 2018-05-17T16:18:03

See below

If you know the center #(x_0,y_0)# and the radius #r# of a circle, you can write its equation as

#(x-x_0)^2+(y-y_0)^2=r^2#

which in your case is

#(x-3)^2+(y+4)^2=16#

you can expand it into

#x^2-6x+9+y^2+8y+16=16#

and simplify/rearrange into

#x^2+y^2-6x+8y+9=0#

Not sure which one you refer to as "standard form", so I hope that one of these calculations fell into it