2x^2+10x-21=0

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Solution for 2x^2+10x-21=0 equation:


Simplifying
2x2 + 10x + -21 = 0

Reorder the terms:
-21 + 10x + 2x2 = 0

Solving
-21 + 10x + 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'.
-10.5 + 5x + x2 = 0

Move the constant term to the right:

Add '10.5' to each side of the equation.
-10.5 + 5x + 10.5 + x2 = 0 + 10.5

Reorder the terms:
-10.5 + 10.5 + 5x + x2 = 0 + 10.5

Combine like terms: -10.5 + 10.5 = 0.0
0.0 + 5x + x2 = 0 + 10.5
5x + x2 = 0 + 10.5

Combine like terms: 0 + 10.5 = 10.5
5x + x2 = 10.5

The x term is 5x.  Take half its coefficient (2.5).
Square it (6.25) and add it to both sides.

Add '6.25' to each side of the equation.
5x + 6.25 + x2 = 10.5 + 6.25

Reorder the terms:
6.25 + 5x + x2 = 10.5 + 6.25

Combine like terms: 10.5 + 6.25 = 16.75
6.25 + 5x + x2 = 16.75

Factor a perfect square on the left side:
(x + 2.5)(x + 2.5) = 16.75

Calculate the square root of the right side: 4.092676386

Break this problem into two subproblems by setting 
(x + 2.5) equal to 4.092676386 and -4.092676386.

Subproblem 1

x + 2.5 = 4.092676386 Simplifying x + 2.5 = 4.092676386 Reorder the terms: 2.5 + x = 4.092676386 Solving 2.5 + x = 4.092676386 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.5' to each side of the equation. 2.5 + -2.5 + x = 4.092676386 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = 4.092676386 + -2.5 x = 4.092676386 + -2.5 Combine like terms: 4.092676386 + -2.5 = 1.592676386 x = 1.592676386 Simplifying x = 1.592676386

Subproblem 2

x + 2.5 = -4.092676386 Simplifying x + 2.5 = -4.092676386 Reorder the terms: 2.5 + x = -4.092676386 Solving 2.5 + x = -4.092676386 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.5' to each side of the equation. 2.5 + -2.5 + x = -4.092676386 + -2.5 Combine like terms: 2.5 + -2.5 = 0.0 0.0 + x = -4.092676386 + -2.5 x = -4.092676386 + -2.5 Combine like terms: -4.092676386 + -2.5 = -6.592676386 x = -6.592676386 Simplifying x = -6.592676386

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.592676386, -6.592676386}

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