5x^2-21x-20=x

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Solution for 5x^2-21x-20=x equation:


Simplifying
5x2 + -21x + -20 = x

Reorder the terms:
-20 + -21x + 5x2 = x

Solving
-20 + -21x + 5x2 = x

Solving for variable 'x'.

Reorder the terms:
-20 + -21x + -1x + 5x2 = x + -1x

Combine like terms: -21x + -1x = -22x
-20 + -22x + 5x2 = x + -1x

Combine like terms: x + -1x = 0
-20 + -22x + 5x2 = 0

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

Divide each side by '5'.
-4 + -4.4x + x2 = 0

Move the constant term to the right:

Add '4' to each side of the equation.
-4 + -4.4x + 4 + x2 = 0 + 4

Reorder the terms:
-4 + 4 + -4.4x + x2 = 0 + 4

Combine like terms: -4 + 4 = 0
0 + -4.4x + x2 = 0 + 4
-4.4x + x2 = 0 + 4

Combine like terms: 0 + 4 = 4
-4.4x + x2 = 4

The x term is -4.4x.  Take half its coefficient (-2.2).
Square it (4.84) and add it to both sides.

Add '4.84' to each side of the equation.
-4.4x + 4.84 + x2 = 4 + 4.84

Reorder the terms:
4.84 + -4.4x + x2 = 4 + 4.84

Combine like terms: 4 + 4.84 = 8.84
4.84 + -4.4x + x2 = 8.84

Factor a perfect square on the left side:
(x + -2.2)(x + -2.2) = 8.84

Calculate the square root of the right side: 2.973213749

Break this problem into two subproblems by setting 
(x + -2.2) equal to 2.973213749 and -2.973213749.

Subproblem 1

x + -2.2 = 2.973213749 Simplifying x + -2.2 = 2.973213749 Reorder the terms: -2.2 + x = 2.973213749 Solving -2.2 + x = 2.973213749 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.2' to each side of the equation. -2.2 + 2.2 + x = 2.973213749 + 2.2 Combine like terms: -2.2 + 2.2 = 0.0 0.0 + x = 2.973213749 + 2.2 x = 2.973213749 + 2.2 Combine like terms: 2.973213749 + 2.2 = 5.173213749 x = 5.173213749 Simplifying x = 5.173213749

Subproblem 2

x + -2.2 = -2.973213749 Simplifying x + -2.2 = -2.973213749 Reorder the terms: -2.2 + x = -2.973213749 Solving -2.2 + x = -2.973213749 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '2.2' to each side of the equation. -2.2 + 2.2 + x = -2.973213749 + 2.2 Combine like terms: -2.2 + 2.2 = 0.0 0.0 + x = -2.973213749 + 2.2 x = -2.973213749 + 2.2 Combine like terms: -2.973213749 + 2.2 = -0.773213749 x = -0.773213749 Simplifying x = -0.773213749

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.173213749, -0.773213749}

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