Question 76361
The area of a circle is given by:
{{{A = (pi)(4x^2+12x+9)}}}
As you probably know,the formula for the area of a circle is:
{{{A = (pi)r^2}}}
Set these two equal to each other:
{{{(pi)r^2 = (pi)(4x^2+12x+9)}}} Divide both sides by {{{(pi)}}}
{{{r^2 = 4x^2+12x+9}}} Now factor the right-hand side.
{{{r^2 = (2x+3)^2}}} Take the square root of both sides.
{{{r = 2x+3}}}