x^2+6.9x=128

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Solution for x^2+6.9x=128 equation:


Simplifying
x2 + 6.9x = 128

Reorder the terms:
6.9x + x2 = 128

Solving
6.9x + x2 = 128

Solving for variable 'x'.

Reorder the terms:
-128 + 6.9x + x2 = 128 + -128

Combine like terms: 128 + -128 = 0
-128 + 6.9x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '128' to each side of the equation.
-128 + 6.9x + 128 + x2 = 0 + 128

Reorder the terms:
-128 + 128 + 6.9x + x2 = 0 + 128

Combine like terms: -128 + 128 = 0
0 + 6.9x + x2 = 0 + 128
6.9x + x2 = 0 + 128

Combine like terms: 0 + 128 = 128
6.9x + x2 = 128

The x term is 6.9x.  Take half its coefficient (3.45).
Square it (11.9025) and add it to both sides.

Add '11.9025' to each side of the equation.
6.9x + 11.9025 + x2 = 128 + 11.9025

Reorder the terms:
11.9025 + 6.9x + x2 = 128 + 11.9025

Combine like terms: 128 + 11.9025 = 139.9025
11.9025 + 6.9x + x2 = 139.9025

Factor a perfect square on the left side:
(x + 3.45)(x + 3.45) = 139.9025

Calculate the square root of the right side: 11.828038722

Break this problem into two subproblems by setting 
(x + 3.45) equal to 11.828038722 and -11.828038722.

Subproblem 1

x + 3.45 = 11.828038722 Simplifying x + 3.45 = 11.828038722 Reorder the terms: 3.45 + x = 11.828038722 Solving 3.45 + x = 11.828038722 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.45' to each side of the equation. 3.45 + -3.45 + x = 11.828038722 + -3.45 Combine like terms: 3.45 + -3.45 = 0.00 0.00 + x = 11.828038722 + -3.45 x = 11.828038722 + -3.45 Combine like terms: 11.828038722 + -3.45 = 8.378038722 x = 8.378038722 Simplifying x = 8.378038722

Subproblem 2

x + 3.45 = -11.828038722 Simplifying x + 3.45 = -11.828038722 Reorder the terms: 3.45 + x = -11.828038722 Solving 3.45 + x = -11.828038722 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.45' to each side of the equation. 3.45 + -3.45 + x = -11.828038722 + -3.45 Combine like terms: 3.45 + -3.45 = 0.00 0.00 + x = -11.828038722 + -3.45 x = -11.828038722 + -3.45 Combine like terms: -11.828038722 + -3.45 = -15.278038722 x = -15.278038722 Simplifying x = -15.278038722

Solution

The solution to the problem is based on the solutions from the subproblems. x = {8.378038722, -15.278038722}

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