2x^2+9x=42

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Solution for 2x^2+9x=42 equation:


Simplifying
2x2 + 9x = 42

Reorder the terms:
9x + 2x2 = 42

Solving
9x + 2x2 = 42

Solving for variable 'x'.

Reorder the terms:
-42 + 9x + 2x2 = 42 + -42

Combine like terms: 42 + -42 = 0
-42 + 9x + 2x2 = 0

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

Divide each side by '2'.
-21 + 4.5x + x2 = 0

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + 4.5x + 21 + x2 = 0 + 21

Reorder the terms:
-21 + 21 + 4.5x + x2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + 4.5x + x2 = 0 + 21
4.5x + x2 = 0 + 21

Combine like terms: 0 + 21 = 21
4.5x + x2 = 21

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 = 21 + 5.0625

Reorder the terms:
5.0625 + 4.5x + x2 = 21 + 5.0625

Combine like terms: 21 + 5.0625 = 26.0625
5.0625 + 4.5x + x2 = 26.0625

Factor a perfect square on the left side:
(x + 2.25)(x + 2.25) = 26.0625

Calculate the square root of the right side: 5.105144464

Break this problem into two subproblems by setting 
(x + 2.25) equal to 5.105144464 and -5.105144464.

Subproblem 1

x + 2.25 = 5.105144464 Simplifying x + 2.25 = 5.105144464 Reorder the terms: 2.25 + x = 5.105144464 Solving 2.25 + x = 5.105144464 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 = 5.105144464 + -2.25 Combine like terms: 2.25 + -2.25 = 0.00 0.00 + x = 5.105144464 + -2.25 x = 5.105144464 + -2.25 Combine like terms: 5.105144464 + -2.25 = 2.855144464 x = 2.855144464 Simplifying x = 2.855144464

Subproblem 2

x + 2.25 = -5.105144464 Simplifying x + 2.25 = -5.105144464 Reorder the terms: 2.25 + x = -5.105144464 Solving 2.25 + x = -5.105144464 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 = -5.105144464 + -2.25 Combine like terms: 2.25 + -2.25 = 0.00 0.00 + x = -5.105144464 + -2.25 x = -5.105144464 + -2.25 Combine like terms: -5.105144464 + -2.25 = -7.355144464 x = -7.355144464 Simplifying x = -7.355144464

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.855144464, -7.355144464}

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