(-2x^2)+9x+15=0

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Solution for (-2x^2)+9x+15=0 equation:


Simplifying
(-2x2) + 9x + 15 = 0

Reorder the terms:
15 + 9x + (-2x2) = 0

Solving
15 + 9x + (-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 + -4.5x + x2 = 0

Move the constant term to the right:

Add '7.5' to each side of the equation.
-7.5 + -4.5x + 7.5 + x2 = 0 + 7.5

Reorder the terms:
-7.5 + 7.5 + -4.5x + x2 = 0 + 7.5

Combine like terms: -7.5 + 7.5 = 0.0
0.0 + -4.5x + x2 = 0 + 7.5
-4.5x + x2 = 0 + 7.5

Combine like terms: 0 + 7.5 = 7.5
-4.5x + x2 = 7.5

The x term is -4.5x.  Take half its coefficient (-2.25).
Square it (5.0625) and add it to both sides.

Add '5.0625' to each side of the equation.
-4.5x + 5.0625 + x2 = 7.5 + 5.0625

Reorder the terms:
5.0625 + -4.5x + x2 = 7.5 + 5.0625

Combine like terms: 7.5 + 5.0625 = 12.5625
5.0625 + -4.5x + x2 = 12.5625

Factor a perfect square on the left side:
((x) + -2.25)((x) + -2.25) = 12.5625

Calculate the square root of the right side: 3.54436172

Break this problem into two subproblems by setting 
((x) + -2.25) equal to 3.54436172 and -3.54436172.

Subproblem 1

(x) + -2.25 = 3.54436172 Simplifying (x) + -2.25 = 3.54436172 x + -2.25 = 3.54436172 Reorder the terms: -2.25 + x = 3.54436172 Solving -2.25 + x = 3.54436172 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.25' to each side of the equation. -2.25 + 2.25 + x = 3.54436172 + 2.25 Combine like terms: -2.25 + 2.25 = 0.00 0.00 + x = 3.54436172 + 2.25 x = 3.54436172 + 2.25 Combine like terms: 3.54436172 + 2.25 = 5.79436172 x = 5.79436172 Simplifying x = 5.79436172

Subproblem 2

(x) + -2.25 = -3.54436172 Simplifying (x) + -2.25 = -3.54436172 x + -2.25 = -3.54436172 Reorder the terms: -2.25 + x = -3.54436172 Solving -2.25 + x = -3.54436172 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.25' to each side of the equation. -2.25 + 2.25 + x = -3.54436172 + 2.25 Combine like terms: -2.25 + 2.25 = 0.00 0.00 + x = -3.54436172 + 2.25 x = -3.54436172 + 2.25 Combine like terms: -3.54436172 + 2.25 = -1.29436172 x = -1.29436172 Simplifying x = -1.29436172

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.79436172, -1.29436172}

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