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

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


Simplifying
-2x2 + 7x + 8 = 0

Reorder the terms:
8 + 7x + -2x2 = 0

Solving
8 + 7x + -2x2 = 0

Solving for variable 'x'.

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

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

Move the constant term to the right:

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

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

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

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

The x term is -3.5x.  Take half its coefficient (-1.75).
Square it (3.0625) and add it to both sides.

Add '3.0625' to each side of the equation.
-3.5x + 3.0625 + x2 = 4 + 3.0625

Reorder the terms:
3.0625 + -3.5x + x2 = 4 + 3.0625

Combine like terms: 4 + 3.0625 = 7.0625
3.0625 + -3.5x + x2 = 7.0625

Factor a perfect square on the left side:
(x + -1.75)(x + -1.75) = 7.0625

Calculate the square root of the right side: 2.657536453

Break this problem into two subproblems by setting 
(x + -1.75) equal to 2.657536453 and -2.657536453.

Subproblem 1

x + -1.75 = 2.657536453 Simplifying x + -1.75 = 2.657536453 Reorder the terms: -1.75 + x = 2.657536453 Solving -1.75 + x = 2.657536453 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.75' to each side of the equation. -1.75 + 1.75 + x = 2.657536453 + 1.75 Combine like terms: -1.75 + 1.75 = 0.00 0.00 + x = 2.657536453 + 1.75 x = 2.657536453 + 1.75 Combine like terms: 2.657536453 + 1.75 = 4.407536453 x = 4.407536453 Simplifying x = 4.407536453

Subproblem 2

x + -1.75 = -2.657536453 Simplifying x + -1.75 = -2.657536453 Reorder the terms: -1.75 + x = -2.657536453 Solving -1.75 + x = -2.657536453 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.75' to each side of the equation. -1.75 + 1.75 + x = -2.657536453 + 1.75 Combine like terms: -1.75 + 1.75 = 0.00 0.00 + x = -2.657536453 + 1.75 x = -2.657536453 + 1.75 Combine like terms: -2.657536453 + 1.75 = -0.907536453 x = -0.907536453 Simplifying x = -0.907536453

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.407536453, -0.907536453}

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