Question 91634
To find the radius, find the distance between (2,0) and (-1,4)


Start with the given distance formula

{{{d=sqrt((x[1]-x[2])^2+(y[1]-y[2])^2)}}} where *[Tex \Large \left(x_{1}, y_{1}\right)] is the first point *[Tex \Large \left(2,0\right)] and *[Tex \Large \left(x_{2}, y_{2}\right)] is the second point *[Tex \Large \left(-1,4\right)]


{{{d=sqrt((2--1)^2+(0-4)^2)}}} Plug in {{{x[1]=2}}}, {{{x[2]=-1}}}, {{{y[1]=0}}}, {{{y[2]=4}}}


{{{d=sqrt((3)^2+(-4)^2)}}} Evaluate {{{2--1}}} to get 3. Evaluate {{{0-4}}} to get -4. 


{{{d=sqrt(9+16)}}} Square each value


{{{d=sqrt(25)}}} Add


{{{d=5}}} Simplify the square root  (note: If you need help with simplifying the square root, check out this <a href=http://www.algebra.com/algebra/homework/Radicals/simplifying-square-roots.solver> solver</a>)


So the distance between (2,0) and (-1,4) is 5 units


So the radius is 5 units