x^2-7x-80=0

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Solution for x^2-7x-80=0 equation:


Simplifying
x2 + -7x + -80 = 0

Reorder the terms:
-80 + -7x + x2 = 0

Solving
-80 + -7x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '80' to each side of the equation.
-80 + -7x + 80 + x2 = 0 + 80

Reorder the terms:
-80 + 80 + -7x + x2 = 0 + 80

Combine like terms: -80 + 80 = 0
0 + -7x + x2 = 0 + 80
-7x + x2 = 0 + 80

Combine like terms: 0 + 80 = 80
-7x + x2 = 80

The x term is -7x.  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.
-7x + 12.25 + x2 = 80 + 12.25

Reorder the terms:
12.25 + -7x + x2 = 80 + 12.25

Combine like terms: 80 + 12.25 = 92.25
12.25 + -7x + x2 = 92.25

Factor a perfect square on the left side:
(x + -3.5)(x + -3.5) = 92.25

Calculate the square root of the right side: 9.604686356

Break this problem into two subproblems by setting 
(x + -3.5) equal to 9.604686356 and -9.604686356.

Subproblem 1

x + -3.5 = 9.604686356 Simplifying x + -3.5 = 9.604686356 Reorder the terms: -3.5 + x = 9.604686356 Solving -3.5 + x = 9.604686356 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = 9.604686356 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = 9.604686356 + 3.5 x = 9.604686356 + 3.5 Combine like terms: 9.604686356 + 3.5 = 13.104686356 x = 13.104686356 Simplifying x = 13.104686356

Subproblem 2

x + -3.5 = -9.604686356 Simplifying x + -3.5 = -9.604686356 Reorder the terms: -3.5 + x = -9.604686356 Solving -3.5 + x = -9.604686356 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '3.5' to each side of the equation. -3.5 + 3.5 + x = -9.604686356 + 3.5 Combine like terms: -3.5 + 3.5 = 0.0 0.0 + x = -9.604686356 + 3.5 x = -9.604686356 + 3.5 Combine like terms: -9.604686356 + 3.5 = -6.104686356 x = -6.104686356 Simplifying x = -6.104686356

Solution

The solution to the problem is based on the solutions from the subproblems. x = {13.104686356, -6.104686356}

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