2x^2+3x-15=9

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Solution for 2x^2+3x-15=9 equation:


Simplifying
2x2 + 3x + -15 = 9

Reorder the terms:
-15 + 3x + 2x2 = 9

Solving
-15 + 3x + 2x2 = 9

Solving for variable 'x'.

Reorder the terms:
-15 + -9 + 3x + 2x2 = 9 + -9

Combine like terms: -15 + -9 = -24
-24 + 3x + 2x2 = 9 + -9

Combine like terms: 9 + -9 = 0
-24 + 3x + 2x2 = 0

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

Divide each side by '2'.
-12 + 1.5x + x2 = 0

Move the constant term to the right:

Add '12' to each side of the equation.
-12 + 1.5x + 12 + x2 = 0 + 12

Reorder the terms:
-12 + 12 + 1.5x + x2 = 0 + 12

Combine like terms: -12 + 12 = 0
0 + 1.5x + x2 = 0 + 12
1.5x + x2 = 0 + 12

Combine like terms: 0 + 12 = 12
1.5x + x2 = 12

The x term is 1.5x.  Take half its coefficient (0.75).
Square it (0.5625) and add it to both sides.

Add '0.5625' to each side of the equation.
1.5x + 0.5625 + x2 = 12 + 0.5625

Reorder the terms:
0.5625 + 1.5x + x2 = 12 + 0.5625

Combine like terms: 12 + 0.5625 = 12.5625
0.5625 + 1.5x + x2 = 12.5625

Factor a perfect square on the left side:
(x + 0.75)(x + 0.75) = 12.5625

Calculate the square root of the right side: 3.54436172

Break this problem into two subproblems by setting 
(x + 0.75) equal to 3.54436172 and -3.54436172.

Subproblem 1

x + 0.75 = 3.54436172 Simplifying x + 0.75 = 3.54436172 Reorder the terms: 0.75 + x = 3.54436172 Solving 0.75 + x = 3.54436172 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.75' to each side of the equation. 0.75 + -0.75 + x = 3.54436172 + -0.75 Combine like terms: 0.75 + -0.75 = 0.00 0.00 + x = 3.54436172 + -0.75 x = 3.54436172 + -0.75 Combine like terms: 3.54436172 + -0.75 = 2.79436172 x = 2.79436172 Simplifying x = 2.79436172

Subproblem 2

x + 0.75 = -3.54436172 Simplifying x + 0.75 = -3.54436172 Reorder the terms: 0.75 + x = -3.54436172 Solving 0.75 + x = -3.54436172 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.75' to each side of the equation. 0.75 + -0.75 + x = -3.54436172 + -0.75 Combine like terms: 0.75 + -0.75 = 0.00 0.00 + x = -3.54436172 + -0.75 x = -3.54436172 + -0.75 Combine like terms: -3.54436172 + -0.75 = -4.29436172 x = -4.29436172 Simplifying x = -4.29436172

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.79436172, -4.29436172}

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