4x^2+8x=15

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Solution for 4x^2+8x=15 equation:


Simplifying
4x2 + 8x = 15

Reorder the terms:
8x + 4x2 = 15

Solving
8x + 4x2 = 15

Solving for variable 'x'.

Reorder the terms:
-15 + 8x + 4x2 = 15 + -15

Combine like terms: 15 + -15 = 0
-15 + 8x + 4x2 = 0

Begin completing the square.  Divide all terms by
4 the coefficient of the squared term: 

Divide each side by '4'.
-3.75 + 2x + x2 = 0

Move the constant term to the right:

Add '3.75' to each side of the equation.
-3.75 + 2x + 3.75 + x2 = 0 + 3.75

Reorder the terms:
-3.75 + 3.75 + 2x + x2 = 0 + 3.75

Combine like terms: -3.75 + 3.75 = 0.00
0.00 + 2x + x2 = 0 + 3.75
2x + x2 = 0 + 3.75

Combine like terms: 0 + 3.75 = 3.75
2x + x2 = 3.75

The x term is 2x.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2x + 1 + x2 = 3.75 + 1

Reorder the terms:
1 + 2x + x2 = 3.75 + 1

Combine like terms: 3.75 + 1 = 4.75
1 + 2x + x2 = 4.75

Factor a perfect square on the left side:
(x + 1)(x + 1) = 4.75

Calculate the square root of the right side: 2.179449472

Break this problem into two subproblems by setting 
(x + 1) equal to 2.179449472 and -2.179449472.

Subproblem 1

x + 1 = 2.179449472 Simplifying x + 1 = 2.179449472 Reorder the terms: 1 + x = 2.179449472 Solving 1 + x = 2.179449472 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = 2.179449472 + -1 Combine like terms: 1 + -1 = 0 0 + x = 2.179449472 + -1 x = 2.179449472 + -1 Combine like terms: 2.179449472 + -1 = 1.179449472 x = 1.179449472 Simplifying x = 1.179449472

Subproblem 2

x + 1 = -2.179449472 Simplifying x + 1 = -2.179449472 Reorder the terms: 1 + x = -2.179449472 Solving 1 + x = -2.179449472 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = -2.179449472 + -1 Combine like terms: 1 + -1 = 0 0 + x = -2.179449472 + -1 x = -2.179449472 + -1 Combine like terms: -2.179449472 + -1 = -3.179449472 x = -3.179449472 Simplifying x = -3.179449472

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.179449472, -3.179449472}

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