0=y^2-y-4

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


Simplifying
0 = y2 + -1y + -4

Reorder the terms:
0 = -4 + -1y + y2

Solving
0 = -4 + -1y + y2

Solving for variable 'y'.

Combine like terms: 0 + 4 = 4
4 + y + -1y2 = -4 + -1y + y2 + 4 + y + -1y2

Reorder the terms:
4 + y + -1y2 = -4 + 4 + -1y + y + y2 + -1y2

Combine like terms: -4 + 4 = 0
4 + y + -1y2 = 0 + -1y + y + y2 + -1y2
4 + y + -1y2 = -1y + y + y2 + -1y2

Combine like terms: -1y + y = 0
4 + y + -1y2 = 0 + y2 + -1y2
4 + y + -1y2 = y2 + -1y2

Combine like terms: y2 + -1y2 = 0
4 + y + -1y2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-4 + -1y + y2 = 0

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + -1y + 4 + y2 = 0 + 4

Reorder the terms:
-4 + 4 + -1y + y2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -1y + y2 = 0 + 4
-1y + y2 = 0 + 4

Combine like terms: 0 + 4 = 4
-1y + y2 = 4

The y term is y.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
-1y + 0.25 + y2 = 4 + 0.25

Reorder the terms:
0.25 + -1y + y2 = 4 + 0.25

Combine like terms: 4 + 0.25 = 4.25
0.25 + -1y + y2 = 4.25

Factor a perfect square on the left side:
(y + 0.5)(y + 0.5) = 4.25

Calculate the square root of the right side: 2.061552813

Break this problem into two subproblems by setting 
(y + 0.5) equal to 2.061552813 and -2.061552813.


Subproblem 1
y + 0.5 = 2.061552813

Simplifying
y + 0.5 = 2.061552813

Reorder the terms:
0.5 + y = 2.061552813

Solving
0.5 + y = 2.061552813

Solving for variable 'y'.

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

Add '-0.5' to each side of the equation.
0.5 + -0.5 + y = 2.061552813 + -0.5

Combine like terms: 0.5 + -0.5 = 0.0
0.0 + y = 2.061552813 + -0.5
y = 2.061552813 + -0.5

Combine like terms: 2.061552813 + -0.5 = 1.561552813
y = 1.561552813

Simplifying
y = 1.561552813


Subproblem 2
y + 0.5 = -2.061552813

Simplifying
y + 0.5 = -2.061552813

Reorder the terms:
0.5 + y = -2.061552813

Solving
0.5 + y = -2.061552813

Solving for variable 'y'.

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

Add '-0.5' to each side of the equation.
0.5 + -0.5 + y = -2.061552813 + -0.5

Combine like terms: 0.5 + -0.5 = 0.0
0.0 + y = -2.061552813 + -0.5
y = -2.061552813 + -0.5

Combine like terms: -2.061552813 + -0.5 = -2.561552813
y = -2.561552813

Simplifying
y = -2.561552813


Solution
The solution to the problem is based on the solutions
from the subproblems.
y = {1.561552813, -2.561552813}

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