y^2-9y-18=0

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Solution for y^2-9y-18=0 equation:


Simplifying
y2 + -9y + -18 = 0

Reorder the terms:
-18 + -9y + y2 = 0

Solving
-18 + -9y + y2 = 0

Solving for variable 'y'.

Begin completing the square.

Move the constant term to the right:

Add '18' to each side of the equation.
-18 + -9y + 18 + y2 = 0 + 18

Reorder the terms:
-18 + 18 + -9y + y2 = 0 + 18

Combine like terms: -18 + 18 = 0
0 + -9y + y2 = 0 + 18
-9y + y2 = 0 + 18

Combine like terms: 0 + 18 = 18
-9y + y2 = 18

The y term is -9y.  Take half its coefficient (-4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
-9y + 20.25 + y2 = 18 + 20.25

Reorder the terms:
20.25 + -9y + y2 = 18 + 20.25

Combine like terms: 18 + 20.25 = 38.25
20.25 + -9y + y2 = 38.25

Factor a perfect square on the left side:
(y + -4.5)(y + -4.5) = 38.25

Calculate the square root of the right side: 6.184658438

Break this problem into two subproblems by setting 
(y + -4.5) equal to 6.184658438 and -6.184658438.

Subproblem 1

y + -4.5 = 6.184658438 Simplifying y + -4.5 = 6.184658438 Reorder the terms: -4.5 + y = 6.184658438 Solving -4.5 + y = 6.184658438 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '4.5' to each side of the equation. -4.5 + 4.5 + y = 6.184658438 + 4.5 Combine like terms: -4.5 + 4.5 = 0.0 0.0 + y = 6.184658438 + 4.5 y = 6.184658438 + 4.5 Combine like terms: 6.184658438 + 4.5 = 10.684658438 y = 10.684658438 Simplifying y = 10.684658438

Subproblem 2

y + -4.5 = -6.184658438 Simplifying y + -4.5 = -6.184658438 Reorder the terms: -4.5 + y = -6.184658438 Solving -4.5 + y = -6.184658438 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '4.5' to each side of the equation. -4.5 + 4.5 + y = -6.184658438 + 4.5 Combine like terms: -4.5 + 4.5 = 0.0 0.0 + y = -6.184658438 + 4.5 y = -6.184658438 + 4.5 Combine like terms: -6.184658438 + 4.5 = -1.684658438 y = -1.684658438 Simplifying y = -1.684658438

Solution

The solution to the problem is based on the solutions from the subproblems. y = {10.684658438, -1.684658438}

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