2x^2-42x=55

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Solution for 2x^2-42x=55 equation:


Simplifying
2x2 + -42x = 55

Reorder the terms:
-42x + 2x2 = 55

Solving
-42x + 2x2 = 55

Solving for variable 'x'.

Reorder the terms:
-55 + -42x + 2x2 = 55 + -55

Combine like terms: 55 + -55 = 0
-55 + -42x + 2x2 = 0

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

Divide each side by '2'.
-27.5 + -21x + x2 = 0

Move the constant term to the right:

Add '27.5' to each side of the equation.
-27.5 + -21x + 27.5 + x2 = 0 + 27.5

Reorder the terms:
-27.5 + 27.5 + -21x + x2 = 0 + 27.5

Combine like terms: -27.5 + 27.5 = 0.0
0.0 + -21x + x2 = 0 + 27.5
-21x + x2 = 0 + 27.5

Combine like terms: 0 + 27.5 = 27.5
-21x + x2 = 27.5

The x term is -21x.  Take half its coefficient (-10.5).
Square it (110.25) and add it to both sides.

Add '110.25' to each side of the equation.
-21x + 110.25 + x2 = 27.5 + 110.25

Reorder the terms:
110.25 + -21x + x2 = 27.5 + 110.25

Combine like terms: 27.5 + 110.25 = 137.75
110.25 + -21x + x2 = 137.75

Factor a perfect square on the left side:
(x + -10.5)(x + -10.5) = 137.75

Calculate the square root of the right side: 11.736694594

Break this problem into two subproblems by setting 
(x + -10.5) equal to 11.736694594 and -11.736694594.

Subproblem 1

x + -10.5 = 11.736694594 Simplifying x + -10.5 = 11.736694594 Reorder the terms: -10.5 + x = 11.736694594 Solving -10.5 + x = 11.736694594 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '10.5' to each side of the equation. -10.5 + 10.5 + x = 11.736694594 + 10.5 Combine like terms: -10.5 + 10.5 = 0.0 0.0 + x = 11.736694594 + 10.5 x = 11.736694594 + 10.5 Combine like terms: 11.736694594 + 10.5 = 22.236694594 x = 22.236694594 Simplifying x = 22.236694594

Subproblem 2

x + -10.5 = -11.736694594 Simplifying x + -10.5 = -11.736694594 Reorder the terms: -10.5 + x = -11.736694594 Solving -10.5 + x = -11.736694594 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '10.5' to each side of the equation. -10.5 + 10.5 + x = -11.736694594 + 10.5 Combine like terms: -10.5 + 10.5 = 0.0 0.0 + x = -11.736694594 + 10.5 x = -11.736694594 + 10.5 Combine like terms: -11.736694594 + 10.5 = -1.236694594 x = -1.236694594 Simplifying x = -1.236694594

Solution

The solution to the problem is based on the solutions from the subproblems. x = {22.236694594, -1.236694594}

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