x^2+8.4x-40=0

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Solution for x^2+8.4x-40=0 equation:


Simplifying
x2 + 8.4x + -40 = 0

Reorder the terms:
-40 + 8.4x + x2 = 0

Solving
-40 + 8.4x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '40' to each side of the equation.
-40 + 8.4x + 40 + x2 = 0 + 40

Reorder the terms:
-40 + 40 + 8.4x + x2 = 0 + 40

Combine like terms: -40 + 40 = 0
0 + 8.4x + x2 = 0 + 40
8.4x + x2 = 0 + 40

Combine like terms: 0 + 40 = 40
8.4x + x2 = 40

The x term is 8.4x.  Take half its coefficient (4.2).
Square it (17.64) and add it to both sides.

Add '17.64' to each side of the equation.
8.4x + 17.64 + x2 = 40 + 17.64

Reorder the terms:
17.64 + 8.4x + x2 = 40 + 17.64

Combine like terms: 40 + 17.64 = 57.64
17.64 + 8.4x + x2 = 57.64

Factor a perfect square on the left side:
(x + 4.2)(x + 4.2) = 57.64

Calculate the square root of the right side: 7.592101158

Break this problem into two subproblems by setting 
(x + 4.2) equal to 7.592101158 and -7.592101158.

Subproblem 1

x + 4.2 = 7.592101158 Simplifying x + 4.2 = 7.592101158 Reorder the terms: 4.2 + x = 7.592101158 Solving 4.2 + x = 7.592101158 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.2' to each side of the equation. 4.2 + -4.2 + x = 7.592101158 + -4.2 Combine like terms: 4.2 + -4.2 = 0.0 0.0 + x = 7.592101158 + -4.2 x = 7.592101158 + -4.2 Combine like terms: 7.592101158 + -4.2 = 3.392101158 x = 3.392101158 Simplifying x = 3.392101158

Subproblem 2

x + 4.2 = -7.592101158 Simplifying x + 4.2 = -7.592101158 Reorder the terms: 4.2 + x = -7.592101158 Solving 4.2 + x = -7.592101158 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.2' to each side of the equation. 4.2 + -4.2 + x = -7.592101158 + -4.2 Combine like terms: 4.2 + -4.2 = 0.0 0.0 + x = -7.592101158 + -4.2 x = -7.592101158 + -4.2 Combine like terms: -7.592101158 + -4.2 = -11.792101158 x = -11.792101158 Simplifying x = -11.792101158

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.392101158, -11.792101158}

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