0=-7x^2+5x+8

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Solution for 0=-7x^2+5x+8 equation:


Simplifying
0 = -7x2 + 5x + 8

Reorder the terms:
0 = 8 + 5x + -7x2

Solving
0 = 8 + 5x + -7x2

Solving for variable 'x'.

Combine like terms: 0 + -8 = -8
-8 + -5x + 7x2 = 8 + 5x + -7x2 + -8 + -5x + 7x2

Reorder the terms:
-8 + -5x + 7x2 = 8 + -8 + 5x + -5x + -7x2 + 7x2

Combine like terms: 8 + -8 = 0
-8 + -5x + 7x2 = 0 + 5x + -5x + -7x2 + 7x2
-8 + -5x + 7x2 = 5x + -5x + -7x2 + 7x2

Combine like terms: 5x + -5x = 0
-8 + -5x + 7x2 = 0 + -7x2 + 7x2
-8 + -5x + 7x2 = -7x2 + 7x2

Combine like terms: -7x2 + 7x2 = 0
-8 + -5x + 7x2 = 0

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

Divide each side by '7'.
-1.142857143 + -0.7142857143x + x2 = 0

Move the constant term to the right:

Add '1.142857143' to each side of the equation.
-1.142857143 + -0.7142857143x + 1.142857143 + x2 = 0 + 1.142857143

Reorder the terms:
-1.142857143 + 1.142857143 + -0.7142857143x + x2 = 0 + 1.142857143

Combine like terms: -1.142857143 + 1.142857143 = 0.000000000
0.000000000 + -0.7142857143x + x2 = 0 + 1.142857143
-0.7142857143x + x2 = 0 + 1.142857143

Combine like terms: 0 + 1.142857143 = 1.142857143
-0.7142857143x + x2 = 1.142857143

The x term is -0.7142857143x.  Take half its coefficient (-0.3571428572).
Square it (0.1275510204) and add it to both sides.

Add '0.1275510204' to each side of the equation.
-0.7142857143x + 0.1275510204 + x2 = 1.142857143 + 0.1275510204

Reorder the terms:
0.1275510204 + -0.7142857143x + x2 = 1.142857143 + 0.1275510204

Combine like terms: 1.142857143 + 0.1275510204 = 1.2704081634
0.1275510204 + -0.7142857143x + x2 = 1.2704081634

Factor a perfect square on the left side:
(x + -0.3571428572)(x + -0.3571428572) = 1.2704081634

Calculate the square root of the right side: 1.127123846

Break this problem into two subproblems by setting 
(x + -0.3571428572) equal to 1.127123846 and -1.127123846.

Subproblem 1

x + -0.3571428572 = 1.127123846 Simplifying x + -0.3571428572 = 1.127123846 Reorder the terms: -0.3571428572 + x = 1.127123846 Solving -0.3571428572 + x = 1.127123846 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.3571428572' to each side of the equation. -0.3571428572 + 0.3571428572 + x = 1.127123846 + 0.3571428572 Combine like terms: -0.3571428572 + 0.3571428572 = 0.0000000000 0.0000000000 + x = 1.127123846 + 0.3571428572 x = 1.127123846 + 0.3571428572 Combine like terms: 1.127123846 + 0.3571428572 = 1.4842667032 x = 1.4842667032 Simplifying x = 1.4842667032

Subproblem 2

x + -0.3571428572 = -1.127123846 Simplifying x + -0.3571428572 = -1.127123846 Reorder the terms: -0.3571428572 + x = -1.127123846 Solving -0.3571428572 + x = -1.127123846 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.3571428572' to each side of the equation. -0.3571428572 + 0.3571428572 + x = -1.127123846 + 0.3571428572 Combine like terms: -0.3571428572 + 0.3571428572 = 0.0000000000 0.0000000000 + x = -1.127123846 + 0.3571428572 x = -1.127123846 + 0.3571428572 Combine like terms: -1.127123846 + 0.3571428572 = -0.7699809888 x = -0.7699809888 Simplifying x = -0.7699809888

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.4842667032, -0.7699809888}

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