A(r)=4*3.14*r^2

Solution for A(r)=4*3.14*r^2 equation:

Simplifying
A(r) = 4 * 3.14r2

Multiply A * r
rA = 4 * 3.14r2

Multiply 4 * 3.14
rA = 12.56r2

Solving
rA = 12.56r2

Solving for variable 'r'.

Combine like terms: 12.56r2 + -12.56r2 = 0.00
rA + -12.56r2 = 0.00

Factor out the Greatest Common Factor (GCF), 'r'.
r(A + -12.56r) = 0.00

Subproblem 1
Set the factor 'r' equal to zero and attempt to solve:

Simplifying
r = 0

Solving
r = 0

Move all terms containing r to the left, all other terms to the right.

Simplifying
r = 0
Subproblem 2
Set the factor '(A + -12.56r)' equal to zero and attempt to solve:

Simplifying
A + -12.56r = 0

Solving
A + -12.56r = 0

Move all terms containing r to the left, all other terms to the right.

Add '-1A' to each side of the equation.
A + -1A + -12.56r = 0 + -1A

Combine like terms: A + -1A = 0
0 + -12.56r = 0 + -1A
-12.56r = 0 + -1A
Remove the zero:
-12.56r = -1A

Divide each side by '-12.56'.
r = 0.07961783439A

Simplifying
r = 0.07961783439A
Solution
r = {0, 0.07961783439A}