r^2+20r=261

Solution for r^2+20r=261 equation:

Simplifying
r2 + 20r = 261

Reorder the terms:
20r + r2 = 261

Solving
20r + r2 = 261

Solving for variable 'r'.

Reorder the terms:
-261 + 20r + r2 = 261 + -261

Combine like terms: 261 + -261 = 0
-261 + 20r + r2 = 0

Factor a trinomial.
(-29 + -1r)(9 + -1r) = 0

Subproblem 1
Set the factor '(-29 + -1r)' equal to zero and attempt to solve:

Simplifying
-29 + -1r = 0

Solving
-29 + -1r = 0

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

Add '29' to each side of the equation.
-29 + 29 + -1r = 0 + 29

Combine like terms: -29 + 29 = 0
0 + -1r = 0 + 29
-1r = 0 + 29

Combine like terms: 0 + 29 = 29
-1r = 29

Divide each side by '-1'.
r = -29

Simplifying
r = -29
Subproblem 2
Set the factor '(9 + -1r)' equal to zero and attempt to solve:

Simplifying
9 + -1r = 0

Solving
9 + -1r = 0

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

Add '-9' to each side of the equation.
9 + -9 + -1r = 0 + -9

Combine like terms: 9 + -9 = 0
0 + -1r = 0 + -9
-1r = 0 + -9

Combine like terms: 0 + -9 = -9
-1r = -9

Divide each side by '-1'.
r = 9

Simplifying
r = 9
Solution
r = {-29, 9}