2x^2+6x=91

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Solution for 2x^2+6x=91 equation:


Simplifying
2x2 + 6x = 91

Reorder the terms:
6x + 2x2 = 91

Solving
6x + 2x2 = 91

Solving for variable 'x'.

Reorder the terms:
-91 + 6x + 2x2 = 91 + -91

Combine like terms: 91 + -91 = 0
-91 + 6x + 2x2 = 0

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

Divide each side by '2'.
-45.5 + 3x + x2 = 0

Move the constant term to the right:

Add '45.5' to each side of the equation.
-45.5 + 3x + 45.5 + x2 = 0 + 45.5

Reorder the terms:
-45.5 + 45.5 + 3x + x2 = 0 + 45.5

Combine like terms: -45.5 + 45.5 = 0.0
0.0 + 3x + x2 = 0 + 45.5
3x + x2 = 0 + 45.5

Combine like terms: 0 + 45.5 = 45.5
3x + x2 = 45.5

The x term is 3x.  Take half its coefficient (1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
3x + 2.25 + x2 = 45.5 + 2.25

Reorder the terms:
2.25 + 3x + x2 = 45.5 + 2.25

Combine like terms: 45.5 + 2.25 = 47.75
2.25 + 3x + x2 = 47.75

Factor a perfect square on the left side:
(x + 1.5)(x + 1.5) = 47.75

Calculate the square root of the right side: 6.910137481

Break this problem into two subproblems by setting 
(x + 1.5) equal to 6.910137481 and -6.910137481.

Subproblem 1

x + 1.5 = 6.910137481 Simplifying x + 1.5 = 6.910137481 Reorder the terms: 1.5 + x = 6.910137481 Solving 1.5 + x = 6.910137481 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = 6.910137481 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = 6.910137481 + -1.5 x = 6.910137481 + -1.5 Combine like terms: 6.910137481 + -1.5 = 5.410137481 x = 5.410137481 Simplifying x = 5.410137481

Subproblem 2

x + 1.5 = -6.910137481 Simplifying x + 1.5 = -6.910137481 Reorder the terms: 1.5 + x = -6.910137481 Solving 1.5 + x = -6.910137481 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.5' to each side of the equation. 1.5 + -1.5 + x = -6.910137481 + -1.5 Combine like terms: 1.5 + -1.5 = 0.0 0.0 + x = -6.910137481 + -1.5 x = -6.910137481 + -1.5 Combine like terms: -6.910137481 + -1.5 = -8.410137481 x = -8.410137481 Simplifying x = -8.410137481

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.410137481, -8.410137481}

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