2x^2-7=8x

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


Simplifying
2x2 + -7 = 8x

Reorder the terms:
-7 + 2x2 = 8x

Solving
-7 + 2x2 = 8x

Solving for variable 'x'.

Reorder the terms:
-7 + -8x + 2x2 = 8x + -8x

Combine like terms: 8x + -8x = 0
-7 + -8x + 2x2 = 0

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

Divide each side by '2'.
-3.5 + -4x + x2 = 0

Move the constant term to the right:

Add '3.5' to each side of the equation.
-3.5 + -4x + 3.5 + x2 = 0 + 3.5

Reorder the terms:
-3.5 + 3.5 + -4x + x2 = 0 + 3.5

Combine like terms: -3.5 + 3.5 = 0.0
0.0 + -4x + x2 = 0 + 3.5
-4x + x2 = 0 + 3.5

Combine like terms: 0 + 3.5 = 3.5
-4x + x2 = 3.5

The x term is -4x.  Take half its coefficient (-2).
Square it (4) and add it to both sides.

Add '4' to each side of the equation.
-4x + 4 + x2 = 3.5 + 4

Reorder the terms:
4 + -4x + x2 = 3.5 + 4

Combine like terms: 3.5 + 4 = 7.5
4 + -4x + x2 = 7.5

Factor a perfect square on the left side:
(x + -2)(x + -2) = 7.5

Calculate the square root of the right side: 2.738612788

Break this problem into two subproblems by setting 
(x + -2) equal to 2.738612788 and -2.738612788.

Subproblem 1

x + -2 = 2.738612788 Simplifying x + -2 = 2.738612788 Reorder the terms: -2 + x = 2.738612788 Solving -2 + x = 2.738612788 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = 2.738612788 + 2 Combine like terms: -2 + 2 = 0 0 + x = 2.738612788 + 2 x = 2.738612788 + 2 Combine like terms: 2.738612788 + 2 = 4.738612788 x = 4.738612788 Simplifying x = 4.738612788

Subproblem 2

x + -2 = -2.738612788 Simplifying x + -2 = -2.738612788 Reorder the terms: -2 + x = -2.738612788 Solving -2 + x = -2.738612788 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2' to each side of the equation. -2 + 2 + x = -2.738612788 + 2 Combine like terms: -2 + 2 = 0 0 + x = -2.738612788 + 2 x = -2.738612788 + 2 Combine like terms: -2.738612788 + 2 = -0.738612788 x = -0.738612788 Simplifying x = -0.738612788

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.738612788, -0.738612788}

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