r(r+4)-77=0

Solution for r(r+4)-77=0 equation:

Simplifying
r(r + 4) + -77 = 0

Reorder the terms:
r(4 + r) + -77 = 0
(4 * r + r * r) + -77 = 0
(4r + r2) + -77 = 0

Reorder the terms:
-77 + 4r + r2 = 0

Solving
-77 + 4r + r2 = 0

Solving for variable 'r'.

Factor a trinomial.
(-11 + -1r)(7 + -1r) = 0

Subproblem 1
Set the factor '(-11 + -1r)' equal to zero and attempt to solve:

Simplifying
-11 + -1r = 0

Solving
-11 + -1r = 0

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

Add '11' to each side of the equation.
-11 + 11 + -1r = 0 + 11

Combine like terms: -11 + 11 = 0
0 + -1r = 0 + 11
-1r = 0 + 11

Combine like terms: 0 + 11 = 11
-1r = 11

Divide each side by '-1'.
r = -11

Simplifying
r = -11
Subproblem 2
Set the factor '(7 + -1r)' equal to zero and attempt to solve:

Simplifying
7 + -1r = 0

Solving
7 + -1r = 0

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

Add '-7' to each side of the equation.
7 + -7 + -1r = 0 + -7

Combine like terms: 7 + -7 = 0
0 + -1r = 0 + -7
-1r = 0 + -7

Combine like terms: 0 + -7 = -7
-1r = -7

Divide each side by '-1'.
r = 7

Simplifying
r = 7
Solution
r = {-11, 7}