8x^2+15x-5=0

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Solution for 8x^2+15x-5=0 equation:


Simplifying
8x2 + 15x + -5 = 0

Reorder the terms:
-5 + 15x + 8x2 = 0

Solving
-5 + 15x + 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'.
-0.625 + 1.875x + x2 = 0

Move the constant term to the right:

Add '0.625' to each side of the equation.
-0.625 + 1.875x + 0.625 + x2 = 0 + 0.625

Reorder the terms:
-0.625 + 0.625 + 1.875x + x2 = 0 + 0.625

Combine like terms: -0.625 + 0.625 = 0.000
0.000 + 1.875x + x2 = 0 + 0.625
1.875x + x2 = 0 + 0.625

Combine like terms: 0 + 0.625 = 0.625
1.875x + x2 = 0.625

The x term is 1.875x.  Take half its coefficient (0.9375).
Square it (0.87890625) and add it to both sides.

Add '0.87890625' to each side of the equation.
1.875x + 0.87890625 + x2 = 0.625 + 0.87890625

Reorder the terms:
0.87890625 + 1.875x + x2 = 0.625 + 0.87890625

Combine like terms: 0.625 + 0.87890625 = 1.50390625
0.87890625 + 1.875x + x2 = 1.50390625

Factor a perfect square on the left side:
(x + 0.9375)(x + 0.9375) = 1.50390625

Calculate the square root of the right side: 1.226338554

Break this problem into two subproblems by setting 
(x + 0.9375) equal to 1.226338554 and -1.226338554.

Subproblem 1

x + 0.9375 = 1.226338554 Simplifying x + 0.9375 = 1.226338554 Reorder the terms: 0.9375 + x = 1.226338554 Solving 0.9375 + x = 1.226338554 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.9375' to each side of the equation. 0.9375 + -0.9375 + x = 1.226338554 + -0.9375 Combine like terms: 0.9375 + -0.9375 = 0.0000 0.0000 + x = 1.226338554 + -0.9375 x = 1.226338554 + -0.9375 Combine like terms: 1.226338554 + -0.9375 = 0.288838554 x = 0.288838554 Simplifying x = 0.288838554

Subproblem 2

x + 0.9375 = -1.226338554 Simplifying x + 0.9375 = -1.226338554 Reorder the terms: 0.9375 + x = -1.226338554 Solving 0.9375 + x = -1.226338554 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.9375' to each side of the equation. 0.9375 + -0.9375 + x = -1.226338554 + -0.9375 Combine like terms: 0.9375 + -0.9375 = 0.0000 0.0000 + x = -1.226338554 + -0.9375 x = -1.226338554 + -0.9375 Combine like terms: -1.226338554 + -0.9375 = -2.163838554 x = -2.163838554 Simplifying x = -2.163838554

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.288838554, -2.163838554}

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