y^2+4y-72=0

Solution for y^2+4y-72=0 equation:

Simplifying
y2 + 4y + -72 = 0

Reorder the terms:
-72 + 4y + y2 = 0

Solving
-72 + 4y + y2 = 0

Solving for variable 'y'.

Begin completing the square.

Move the constant term to the right:

Add '72' to each side of the equation.
-72 + 4y + 72 + y2 = 0 + 72

Reorder the terms:
-72 + 72 + 4y + y2 = 0 + 72

Combine like terms: -72 + 72 = 0
0 + 4y + y2 = 0 + 72
4y + y2 = 0 + 72

Combine like terms: 0 + 72 = 72
4y + y2 = 72

The y term is 4y.  Take half its coefficient (2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
4y + 4 + y2 = 72 + 4

Reorder the terms:
4 + 4y + y2 = 72 + 4

Combine like terms: 72 + 4 = 76
4 + 4y + y2 = 76

Factor a perfect square on the left side:
(y + 2)(y + 2) = 76

Calculate the square root of the right side: 8.717797887

Break this problem into two subproblems by setting 
(y + 2) equal to 8.717797887 and -8.717797887.

Subproblem 1
y + 2 = 8.717797887

Simplifying
y + 2 = 8.717797887

Reorder the terms:
2 + y = 8.717797887

Solving
2 + y = 8.717797887

Solving for variable 'y'.

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

Add '-2' to each side of the equation.
2 + -2 + y = 8.717797887 + -2

Combine like terms: 2 + -2 = 0
0 + y = 8.717797887 + -2
y = 8.717797887 + -2

Combine like terms: 8.717797887 + -2 = 6.717797887
y = 6.717797887

Simplifying
y = 6.717797887

Subproblem 2
y + 2 = -8.717797887

Simplifying
y + 2 = -8.717797887

Reorder the terms:
2 + y = -8.717797887

Solving
2 + y = -8.717797887

Solving for variable 'y'.

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

Add '-2' to each side of the equation.
2 + -2 + y = -8.717797887 + -2

Combine like terms: 2 + -2 = 0
0 + y = -8.717797887 + -2
y = -8.717797887 + -2

Combine like terms: -8.717797887 + -2 = -10.717797887
y = -10.717797887

Simplifying
y = -10.717797887

Solution
The solution to the problem is based on the solutions
from the subproblems.
y = {6.717797887, -10.717797887}