y^2-3y-8=0

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Solution for y^2-3y-8=0 equation:


Simplifying
y2 + -3y + -8 = 0

Reorder the terms:
-8 + -3y + y2 = 0

Solving
-8 + -3y + y2 = 0

Solving for variable 'y'.

Begin completing the square.

Move the constant term to the right:

Add '8' to each side of the equation.
-8 + -3y + 8 + y2 = 0 + 8

Reorder the terms:
-8 + 8 + -3y + y2 = 0 + 8

Combine like terms: -8 + 8 = 0
0 + -3y + y2 = 0 + 8
-3y + y2 = 0 + 8

Combine like terms: 0 + 8 = 8
-3y + y2 = 8

The y term is -3y.  Take half its coefficient (-1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
-3y + 2.25 + y2 = 8 + 2.25

Reorder the terms:
2.25 + -3y + y2 = 8 + 2.25

Combine like terms: 8 + 2.25 = 10.25
2.25 + -3y + y2 = 10.25

Factor a perfect square on the left side:
(y + -1.5)(y + -1.5) = 10.25

Calculate the square root of the right side: 3.201562119

Break this problem into two subproblems by setting 
(y + -1.5) equal to 3.201562119 and -3.201562119.

Subproblem 1

y + -1.5 = 3.201562119 Simplifying y + -1.5 = 3.201562119 Reorder the terms: -1.5 + y = 3.201562119 Solving -1.5 + y = 3.201562119 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + y = 3.201562119 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + y = 3.201562119 + 1.5 y = 3.201562119 + 1.5 Combine like terms: 3.201562119 + 1.5 = 4.701562119 y = 4.701562119 Simplifying y = 4.701562119

Subproblem 2

y + -1.5 = -3.201562119 Simplifying y + -1.5 = -3.201562119 Reorder the terms: -1.5 + y = -3.201562119 Solving -1.5 + y = -3.201562119 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + y = -3.201562119 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + y = -3.201562119 + 1.5 y = -3.201562119 + 1.5 Combine like terms: -3.201562119 + 1.5 = -1.701562119 y = -1.701562119 Simplifying y = -1.701562119

Solution

The solution to the problem is based on the solutions from the subproblems. y = {4.701562119, -1.701562119}

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