Question

What is a radius of a circle given by the equation x²-2x+8y-47=0

Answer 1

First, we are going to rewrite it as a parabola equation.
Rewrite.
$8y=-x^2+2x+47$
Divide by 8.
$y=-\frac{x^2}{8}+\frac{x}{4}+\frac{47}{8}$
Factor out coefficient.
$y=-\frac{1}{8}\left(x^2-2x\right)+\frac{47}{8}$
Then, we are going to convert x into square form.
$y=-\frac{1}{8}\left(x^2-2x+1\right)+\frac{1}{8}\cdot \:1+\frac{47}{8}$
Convert the whole expression into square form.
$y=-\frac{1}{8}\left(x-1\right)^2+\frac{1}{8}\cdot \:1+\frac{47}{8}$
Simplify.
$y=-\frac{1}{8}\left(x-1\right)^2+6$
Subtract 6 from both sides.
$y-6=-\frac{1}{8}\left(x-1\right)^2$
Divide by coefficient.
$-8\left(y-6\right)=\left(x-1\right)^2$
Rewrite in standard form.
$4\left(-2\right)\left(y-6\right)=\left(x-1\right)^2$

The radius of the circle will be -2. Also, no matter what the sign says, the radius has to always be positive. 
Have a nice day! :)

Answer 2

Answer: the radius is 8 units

Step-by-step explanation: