-2x^2+6x+15=0

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Solution for -2x^2+6x+15=0 equation:


Simplifying
-2x2 + 6x + 15 = 0

Reorder the terms:
15 + 6x + -2x2 = 0

Solving
15 + 6x + -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'.
-7.5 + -3x + x2 = 0

Move the constant term to the right:

Add '7.5' to each side of the equation.
-7.5 + -3x + 7.5 + x2 = 0 + 7.5

Reorder the terms:
-7.5 + 7.5 + -3x + x2 = 0 + 7.5

Combine like terms: -7.5 + 7.5 = 0.0
0.0 + -3x + x2 = 0 + 7.5
-3x + x2 = 0 + 7.5

Combine like terms: 0 + 7.5 = 7.5
-3x + x2 = 7.5

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 = 7.5 + 2.25

Reorder the terms:
2.25 + -3x + x2 = 7.5 + 2.25

Combine like terms: 7.5 + 2.25 = 9.75
2.25 + -3x + x2 = 9.75

Factor a perfect square on the left side:
(x + -1.5)(x + -1.5) = 9.75

Calculate the square root of the right side: 3.122498999

Break this problem into two subproblems by setting 
(x + -1.5) equal to 3.122498999 and -3.122498999.

Subproblem 1

x + -1.5 = 3.122498999 Simplifying x + -1.5 = 3.122498999 Reorder the terms: -1.5 + x = 3.122498999 Solving -1.5 + x = 3.122498999 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 = 3.122498999 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x = 3.122498999 + 1.5 x = 3.122498999 + 1.5 Combine like terms: 3.122498999 + 1.5 = 4.622498999 x = 4.622498999 Simplifying x = 4.622498999

Subproblem 2

x + -1.5 = -3.122498999 Simplifying x + -1.5 = -3.122498999 Reorder the terms: -1.5 + x = -3.122498999 Solving -1.5 + x = -3.122498999 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 = -3.122498999 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x = -3.122498999 + 1.5 x = -3.122498999 + 1.5 Combine like terms: -3.122498999 + 1.5 = -1.622498999 x = -1.622498999 Simplifying x = -1.622498999

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.622498999, -1.622498999}

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