800=3.14r^2(8)

Solution for 800=3.14r^2(8) equation:

Simplifying
800 = 3.14r2(8)

Reorder the terms for easier multiplication:
800 = 3.14 * 8r2

Multiply 3.14 * 8
800 = 25.12r2

Solving
800 = 25.12r2

Solving for variable 'r'.

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

Add '-25.12r2' to each side of the equation.
800 + -25.12r2 = 25.12r2 + -25.12r2

Combine like terms: 25.12r2 + -25.12r2 = 0.00
800 + -25.12r2 = 0.00

Add '-800' to each side of the equation.
800 + -800 + -25.12r2 = 0.00 + -800

Combine like terms: 800 + -800 = 0
0 + -25.12r2 = 0.00 + -800
-25.12r2 = 0.00 + -800

Combine like terms: 0.00 + -800 = -800
-25.12r2 = -800

Divide each side by '-25.12'.
r2 = 31.84713376

Simplifying
r2 = 31.84713376

Take the square root of each side:
r = {-5.64332648, 5.64332648}