x^2+5x=80

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Solution for x^2+5x=80 equation:


Simplifying
x2 + 5x = 80

Reorder the terms:
5x + x2 = 80

Solving
5x + x2 = 80

Solving for variable 'x'.

Reorder the terms:
-80 + 5x + x2 = 80 + -80

Combine like terms: 80 + -80 = 0
-80 + 5x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '80' to each side of the equation.
-80 + 5x + 80 + x2 = 0 + 80

Reorder the terms:
-80 + 80 + 5x + x2 = 0 + 80

Combine like terms: -80 + 80 = 0
0 + 5x + x2 = 0 + 80
5x + x2 = 0 + 80

Combine like terms: 0 + 80 = 80
5x + x2 = 80

The x term is 5x.  Take half its coefficient (2.5).
Square it (6.25) and add it to both sides.

Add '6.25' to each side of the equation.
5x + 6.25 + x2 = 80 + 6.25

Reorder the terms:
6.25 + 5x + x2 = 80 + 6.25

Combine like terms: 80 + 6.25 = 86.25
6.25 + 5x + x2 = 86.25

Factor a perfect square on the left side:
(x + 2.5)(x + 2.5) = 86.25

Calculate the square root of the right side: 9.287087811

Break this problem into two subproblems by setting 
(x + 2.5) equal to 9.287087811 and -9.287087811.

Subproblem 1

x + 2.5 = 9.287087811 Simplifying x + 2.5 = 9.287087811 Reorder the terms: 2.5 + x = 9.287087811 Solving 2.5 + x = 9.287087811 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.5' to each side of the equation. 2.5 + -2.5 + x = 9.287087811 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = 9.287087811 + -2.5 x = 9.287087811 + -2.5 Combine like terms: 9.287087811 + -2.5 = 6.787087811 x = 6.787087811 Simplifying x = 6.787087811

Subproblem 2

x + 2.5 = -9.287087811 Simplifying x + 2.5 = -9.287087811 Reorder the terms: 2.5 + x = -9.287087811 Solving 2.5 + x = -9.287087811 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.5' to each side of the equation. 2.5 + -2.5 + x = -9.287087811 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = -9.287087811 + -2.5 x = -9.287087811 + -2.5 Combine like terms: -9.287087811 + -2.5 = -11.787087811 x = -11.787087811 Simplifying x = -11.787087811

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.787087811, -11.787087811}

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