y^2-15y-30=0

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Solution for y^2-15y-30=0 equation:


Simplifying
y2 + -15y + -30 = 0

Reorder the terms:
-30 + -15y + y2 = 0

Solving
-30 + -15y + y2 = 0

Solving for variable 'y'.

Begin completing the square.

Move the constant term to the right:

Add '30' to each side of the equation.
-30 + -15y + 30 + y2 = 0 + 30

Reorder the terms:
-30 + 30 + -15y + y2 = 0 + 30

Combine like terms: -30 + 30 = 0
0 + -15y + y2 = 0 + 30
-15y + y2 = 0 + 30

Combine like terms: 0 + 30 = 30
-15y + y2 = 30

The y term is -15y.  Take half its coefficient (-7.5).
Square it (56.25) and add it to both sides.

Add '56.25' to each side of the equation.
-15y + 56.25 + y2 = 30 + 56.25

Reorder the terms:
56.25 + -15y + y2 = 30 + 56.25

Combine like terms: 30 + 56.25 = 86.25
56.25 + -15y + y2 = 86.25

Factor a perfect square on the left side:
(y + -7.5)(y + -7.5) = 86.25

Calculate the square root of the right side: 9.287087811

Break this problem into two subproblems by setting 
(y + -7.5) equal to 9.287087811 and -9.287087811.

Subproblem 1

y + -7.5 = 9.287087811 Simplifying y + -7.5 = 9.287087811 Reorder the terms: -7.5 + y = 9.287087811 Solving -7.5 + y = 9.287087811 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '7.5' to each side of the equation. -7.5 + 7.5 + y = 9.287087811 + 7.5 Combine like terms: -7.5 + 7.5 = 0.0 0.0 + y = 9.287087811 + 7.5 y = 9.287087811 + 7.5 Combine like terms: 9.287087811 + 7.5 = 16.787087811 y = 16.787087811 Simplifying y = 16.787087811

Subproblem 2

y + -7.5 = -9.287087811 Simplifying y + -7.5 = -9.287087811 Reorder the terms: -7.5 + y = -9.287087811 Solving -7.5 + y = -9.287087811 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '7.5' to each side of the equation. -7.5 + 7.5 + y = -9.287087811 + 7.5 Combine like terms: -7.5 + 7.5 = 0.0 0.0 + y = -9.287087811 + 7.5 y = -9.287087811 + 7.5 Combine like terms: -9.287087811 + 7.5 = -1.787087811 y = -1.787087811 Simplifying y = -1.787087811

Solution

The solution to the problem is based on the solutions from the subproblems. y = {16.787087811, -1.787087811}

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