8x^2-7x-9=0

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Solution for 8x^2-7x-9=0 equation:


Simplifying
8x2 + -7x + -9 = 0

Reorder the terms:
-9 + -7x + 8x2 = 0

Solving
-9 + -7x + 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 + -0.875x + x2 = 0

Move the constant term to the right:

Add '1.125' to each side of the equation.
-1.125 + -0.875x + 1.125 + x2 = 0 + 1.125

Reorder the terms:
-1.125 + 1.125 + -0.875x + x2 = 0 + 1.125

Combine like terms: -1.125 + 1.125 = 0.000
0.000 + -0.875x + x2 = 0 + 1.125
-0.875x + x2 = 0 + 1.125

Combine like terms: 0 + 1.125 = 1.125
-0.875x + x2 = 1.125

The x term is -0.875x.  Take half its coefficient (-0.4375).
Square it (0.19140625) and add it to both sides.

Add '0.19140625' to each side of the equation.
-0.875x + 0.19140625 + x2 = 1.125 + 0.19140625

Reorder the terms:
0.19140625 + -0.875x + x2 = 1.125 + 0.19140625

Combine like terms: 1.125 + 0.19140625 = 1.31640625
0.19140625 + -0.875x + x2 = 1.31640625

Factor a perfect square on the left side:
(x + -0.4375)(x + -0.4375) = 1.31640625

Calculate the square root of the right side: 1.147347484

Break this problem into two subproblems by setting 
(x + -0.4375) equal to 1.147347484 and -1.147347484.

Subproblem 1

x + -0.4375 = 1.147347484 Simplifying x + -0.4375 = 1.147347484 Reorder the terms: -0.4375 + x = 1.147347484 Solving -0.4375 + x = 1.147347484 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4375' to each side of the equation. -0.4375 + 0.4375 + x = 1.147347484 + 0.4375 Combine like terms: -0.4375 + 0.4375 = 0.0000 0.0000 + x = 1.147347484 + 0.4375 x = 1.147347484 + 0.4375 Combine like terms: 1.147347484 + 0.4375 = 1.584847484 x = 1.584847484 Simplifying x = 1.584847484

Subproblem 2

x + -0.4375 = -1.147347484 Simplifying x + -0.4375 = -1.147347484 Reorder the terms: -0.4375 + x = -1.147347484 Solving -0.4375 + x = -1.147347484 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4375' to each side of the equation. -0.4375 + 0.4375 + x = -1.147347484 + 0.4375 Combine like terms: -0.4375 + 0.4375 = 0.0000 0.0000 + x = -1.147347484 + 0.4375 x = -1.147347484 + 0.4375 Combine like terms: -1.147347484 + 0.4375 = -0.709847484 x = -0.709847484 Simplifying x = -0.709847484

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.584847484, -0.709847484}

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