How do you write an equation of a circle whose center (-1, 2) and radius 4?

1 Answer
May 15, 2016

Answer:

#(x+1)^2+(y-2)^2=16#

Explanation:

The general equation of a circle with center #(color(red)(a),color(blue)(b))# and radius #color(green)(r)# is
#color(white)("XXX")(x-color(red)(a))^2+(y-color(blue)(b))^2=color(green)(r)^2#

Given #(color(red)(a),color(blue)(b))=(color(red)(-1),color(blue)(2))#
and #color(green)(r)=color(green)(4)#
this becomes
#color(white)("XXX")(x-(color(red)(-1)))^2+(y-color(blue)(2))^2=4^2#

which would normally be simplified as
#color(white)("XXX")(x+1)^2+(y-2)^2=16#