y^2-7y-9=0

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Solution for y^2-7y-9=0 equation:


Simplifying
y2 + -7y + -9 = 0

Reorder the terms:
-9 + -7y + y2 = 0

Solving
-9 + -7y + y2 = 0

Solving for variable 'y'.

Begin completing the square.

Move the constant term to the right:

Add '9' to each side of the equation.
-9 + -7y + 9 + y2 = 0 + 9

Reorder the terms:
-9 + 9 + -7y + y2 = 0 + 9

Combine like terms: -9 + 9 = 0
0 + -7y + y2 = 0 + 9
-7y + y2 = 0 + 9

Combine like terms: 0 + 9 = 9
-7y + y2 = 9

The y term is -7y.  Take half its coefficient (-3.5).
Square it (12.25) and add it to both sides.

Add '12.25' to each side of the equation.
-7y + 12.25 + y2 = 9 + 12.25

Reorder the terms:
12.25 + -7y + y2 = 9 + 12.25

Combine like terms: 9 + 12.25 = 21.25
12.25 + -7y + y2 = 21.25

Factor a perfect square on the left side:
(y + -3.5)(y + -3.5) = 21.25

Calculate the square root of the right side: 4.609772229

Break this problem into two subproblems by setting 
(y + -3.5) equal to 4.609772229 and -4.609772229.

Subproblem 1

y + -3.5 = 4.609772229 Simplifying y + -3.5 = 4.609772229 Reorder the terms: -3.5 + y = 4.609772229 Solving -3.5 + y = 4.609772229 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + y = 4.609772229 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + y = 4.609772229 + 3.5 y = 4.609772229 + 3.5 Combine like terms: 4.609772229 + 3.5 = 8.109772229 y = 8.109772229 Simplifying y = 8.109772229

Subproblem 2

y + -3.5 = -4.609772229 Simplifying y + -3.5 = -4.609772229 Reorder the terms: -3.5 + y = -4.609772229 Solving -3.5 + y = -4.609772229 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + y = -4.609772229 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + y = -4.609772229 + 3.5 y = -4.609772229 + 3.5 Combine like terms: -4.609772229 + 3.5 = -1.109772229 y = -1.109772229 Simplifying y = -1.109772229

Solution

The solution to the problem is based on the solutions from the subproblems. y = {8.109772229, -1.109772229}

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