y^2-y-120=0

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Solution for y^2-y-120=0 equation:


Simplifying
y2 + -1y + -120 = 0

Reorder the terms:
-120 + -1y + y2 = 0

Solving
-120 + -1y + y2 = 0

Solving for variable 'y'.

Begin completing the square.

Move the constant term to the right:

Add '120' to each side of the equation.
-120 + -1y + 120 + y2 = 0 + 120

Reorder the terms:
-120 + 120 + -1y + y2 = 0 + 120

Combine like terms: -120 + 120 = 0
0 + -1y + y2 = 0 + 120
-1y + y2 = 0 + 120

Combine like terms: 0 + 120 = 120
-1y + y2 = 120

The y term is -1y.  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 = 120 + 0.25

Reorder the terms:
0.25 + -1y + y2 = 120 + 0.25

Combine like terms: 120 + 0.25 = 120.25
0.25 + -1y + y2 = 120.25

Factor a perfect square on the left side:
(y + -0.5)(y + -0.5) = 120.25

Calculate the square root of the right side: 10.9658561

Break this problem into two subproblems by setting 
(y + -0.5) equal to 10.9658561 and -10.9658561.

Subproblem 1

y + -0.5 = 10.9658561 Simplifying y + -0.5 = 10.9658561 Reorder the terms: -0.5 + y = 10.9658561 Solving -0.5 + y = 10.9658561 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 = 10.9658561 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + y = 10.9658561 + 0.5 y = 10.9658561 + 0.5 Combine like terms: 10.9658561 + 0.5 = 11.4658561 y = 11.4658561 Simplifying y = 11.4658561

Subproblem 2

y + -0.5 = -10.9658561 Simplifying y + -0.5 = -10.9658561 Reorder the terms: -0.5 + y = -10.9658561 Solving -0.5 + y = -10.9658561 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 = -10.9658561 + 0.5 Combine like terms: -0.5 + 0.5 = 0.0 0.0 + y = -10.9658561 + 0.5 y = -10.9658561 + 0.5 Combine like terms: -10.9658561 + 0.5 = -10.4658561 y = -10.4658561 Simplifying y = -10.4658561

Solution

The solution to the problem is based on the solutions from the subproblems. y = {11.4658561, -10.4658561}

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