y^2+8y=45

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Solution for y^2+8y=45 equation:


Simplifying
y2 + 8y = 45

Reorder the terms:
8y + y2 = 45

Solving
8y + y2 = 45

Solving for variable 'y'.

Reorder the terms:
-45 + 8y + y2 = 45 + -45

Combine like terms: 45 + -45 = 0
-45 + 8y + y2 = 0

Begin completing the square.

Move the constant term to the right:

Add '45' to each side of the equation.
-45 + 8y + 45 + y2 = 0 + 45

Reorder the terms:
-45 + 45 + 8y + y2 = 0 + 45

Combine like terms: -45 + 45 = 0
0 + 8y + y2 = 0 + 45
8y + y2 = 0 + 45

Combine like terms: 0 + 45 = 45
8y + y2 = 45

The y term is 8y.  Take half its coefficient (4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
8y + 16 + y2 = 45 + 16

Reorder the terms:
16 + 8y + y2 = 45 + 16

Combine like terms: 45 + 16 = 61
16 + 8y + y2 = 61

Factor a perfect square on the left side:
(y + 4)(y + 4) = 61

Calculate the square root of the right side: 7.810249676

Break this problem into two subproblems by setting 
(y + 4) equal to 7.810249676 and -7.810249676.

Subproblem 1

y + 4 = 7.810249676 Simplifying y + 4 = 7.810249676 Reorder the terms: 4 + y = 7.810249676 Solving 4 + y = 7.810249676 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + y = 7.810249676 + -4 Combine like terms: 4 + -4 = 0 0 + y = 7.810249676 + -4 y = 7.810249676 + -4 Combine like terms: 7.810249676 + -4 = 3.810249676 y = 3.810249676 Simplifying y = 3.810249676

Subproblem 2

y + 4 = -7.810249676 Simplifying y + 4 = -7.810249676 Reorder the terms: 4 + y = -7.810249676 Solving 4 + y = -7.810249676 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + y = -7.810249676 + -4 Combine like terms: 4 + -4 = 0 0 + y = -7.810249676 + -4 y = -7.810249676 + -4 Combine like terms: -7.810249676 + -4 = -11.810249676 y = -11.810249676 Simplifying y = -11.810249676

Solution

The solution to the problem is based on the solutions from the subproblems. y = {3.810249676, -11.810249676}

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