-8x^2+15x+9=0

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Solution for -8x^2+15x+9=0 equation:


Simplifying
-8x2 + 15x + 9 = 0

Reorder the terms:
9 + 15x + -8x2 = 0

Solving
9 + 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'.
-1.125 + -1.875x + x2 = 0

Move the constant term to the right:

Add '1.125' to each side of the equation.
-1.125 + -1.875x + 1.125 + x2 = 0 + 1.125

Reorder the terms:
-1.125 + 1.125 + -1.875x + x2 = 0 + 1.125

Combine like terms: -1.125 + 1.125 = 0.000
0.000 + -1.875x + x2 = 0 + 1.125
-1.875x + x2 = 0 + 1.125

Combine like terms: 0 + 1.125 = 1.125
-1.875x + x2 = 1.125

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 = 1.125 + 0.87890625

Reorder the terms:
0.87890625 + -1.875x + x2 = 1.125 + 0.87890625

Combine like terms: 1.125 + 0.87890625 = 2.00390625
0.87890625 + -1.875x + x2 = 2.00390625

Factor a perfect square on the left side:
(x + -0.9375)(x + -0.9375) = 2.00390625

Calculate the square root of the right side: 1.415593957

Break this problem into two subproblems by setting 
(x + -0.9375) equal to 1.415593957 and -1.415593957.

Subproblem 1

x + -0.9375 = 1.415593957 Simplifying x + -0.9375 = 1.415593957 Reorder the terms: -0.9375 + x = 1.415593957 Solving -0.9375 + x = 1.415593957 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 = 1.415593957 + 0.9375 Combine like terms: -0.9375 + 0.9375 = 0.0000 0.0000 + x = 1.415593957 + 0.9375 x = 1.415593957 + 0.9375 Combine like terms: 1.415593957 + 0.9375 = 2.353093957 x = 2.353093957 Simplifying x = 2.353093957

Subproblem 2

x + -0.9375 = -1.415593957 Simplifying x + -0.9375 = -1.415593957 Reorder the terms: -0.9375 + x = -1.415593957 Solving -0.9375 + x = -1.415593957 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 = -1.415593957 + 0.9375 Combine like terms: -0.9375 + 0.9375 = 0.0000 0.0000 + x = -1.415593957 + 0.9375 x = -1.415593957 + 0.9375 Combine like terms: -1.415593957 + 0.9375 = -0.478093957 x = -0.478093957 Simplifying x = -0.478093957

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.353093957, -0.478093957}

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