8x^2+4x-15=0

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Solution for 8x^2+4x-15=0 equation:


Simplifying
8x2 + 4x + -15 = 0

Reorder the terms:
-15 + 4x + 8x2 = 0

Solving
-15 + 4x + 8x2 = 0

Solving for variable 'x'.

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

Divide each side by '8'.
-1.875 + 0.5x + x2 = 0

Move the constant term to the right:

Add '1.875' to each side of the equation.
-1.875 + 0.5x + 1.875 + x2 = 0 + 1.875

Reorder the terms:
-1.875 + 1.875 + 0.5x + x2 = 0 + 1.875

Combine like terms: -1.875 + 1.875 = 0.000
0.000 + 0.5x + x2 = 0 + 1.875
0.5x + x2 = 0 + 1.875

Combine like terms: 0 + 1.875 = 1.875
0.5x + x2 = 1.875

The x term is 0.5x.  Take half its coefficient (0.25).
Square it (0.0625) and add it to both sides.

Add '0.0625' to each side of the equation.
0.5x + 0.0625 + x2 = 1.875 + 0.0625

Reorder the terms:
0.0625 + 0.5x + x2 = 1.875 + 0.0625

Combine like terms: 1.875 + 0.0625 = 1.9375
0.0625 + 0.5x + x2 = 1.9375

Factor a perfect square on the left side:
(x + 0.25)(x + 0.25) = 1.9375

Calculate the square root of the right side: 1.391941091

Break this problem into two subproblems by setting 
(x + 0.25) equal to 1.391941091 and -1.391941091.

Subproblem 1

x + 0.25 = 1.391941091 Simplifying x + 0.25 = 1.391941091 Reorder the terms: 0.25 + x = 1.391941091 Solving 0.25 + x = 1.391941091 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.25' to each side of the equation. 0.25 + -0.25 + x = 1.391941091 + -0.25 Combine like terms: 0.25 + -0.25 = 0.00 0.00 + x = 1.391941091 + -0.25 x = 1.391941091 + -0.25 Combine like terms: 1.391941091 + -0.25 = 1.141941091 x = 1.141941091 Simplifying x = 1.141941091

Subproblem 2

x + 0.25 = -1.391941091 Simplifying x + 0.25 = -1.391941091 Reorder the terms: 0.25 + x = -1.391941091 Solving 0.25 + x = -1.391941091 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.25' to each side of the equation. 0.25 + -0.25 + x = -1.391941091 + -0.25 Combine like terms: 0.25 + -0.25 = 0.00 0.00 + x = -1.391941091 + -0.25 x = -1.391941091 + -0.25 Combine like terms: -1.391941091 + -0.25 = -1.641941091 x = -1.641941091 Simplifying x = -1.641941091

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.141941091, -1.641941091}

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