10x^2-21x-21=0

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Solution for 10x^2-21x-21=0 equation:


Simplifying
10x2 + -21x + -21 = 0

Reorder the terms:
-21 + -21x + 10x2 = 0

Solving
-21 + -21x + 10x2 = 0

Solving for variable 'x'.

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

Divide each side by '10'.
-2.1 + -2.1x + x2 = 0

Move the constant term to the right:

Add '2.1' to each side of the equation.
-2.1 + -2.1x + 2.1 + x2 = 0 + 2.1

Reorder the terms:
-2.1 + 2.1 + -2.1x + x2 = 0 + 2.1

Combine like terms: -2.1 + 2.1 = 0.0
0.0 + -2.1x + x2 = 0 + 2.1
-2.1x + x2 = 0 + 2.1

Combine like terms: 0 + 2.1 = 2.1
-2.1x + x2 = 2.1

The x term is -2.1x.  Take half its coefficient (-1.05).
Square it (1.1025) and add it to both sides.

Add '1.1025' to each side of the equation.
-2.1x + 1.1025 + x2 = 2.1 + 1.1025

Reorder the terms:
1.1025 + -2.1x + x2 = 2.1 + 1.1025

Combine like terms: 2.1 + 1.1025 = 3.2025
1.1025 + -2.1x + x2 = 3.2025

Factor a perfect square on the left side:
(x + -1.05)(x + -1.05) = 3.2025

Calculate the square root of the right side: 1.789553017

Break this problem into two subproblems by setting 
(x + -1.05) equal to 1.789553017 and -1.789553017.

Subproblem 1

x + -1.05 = 1.789553017 Simplifying x + -1.05 = 1.789553017 Reorder the terms: -1.05 + x = 1.789553017 Solving -1.05 + x = 1.789553017 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.05' to each side of the equation. -1.05 + 1.05 + x = 1.789553017 + 1.05 Combine like terms: -1.05 + 1.05 = 0.00 0.00 + x = 1.789553017 + 1.05 x = 1.789553017 + 1.05 Combine like terms: 1.789553017 + 1.05 = 2.839553017 x = 2.839553017 Simplifying x = 2.839553017

Subproblem 2

x + -1.05 = -1.789553017 Simplifying x + -1.05 = -1.789553017 Reorder the terms: -1.05 + x = -1.789553017 Solving -1.05 + x = -1.789553017 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.05' to each side of the equation. -1.05 + 1.05 + x = -1.789553017 + 1.05 Combine like terms: -1.05 + 1.05 = 0.00 0.00 + x = -1.789553017 + 1.05 x = -1.789553017 + 1.05 Combine like terms: -1.789553017 + 1.05 = -0.739553017 x = -0.739553017 Simplifying x = -0.739553017

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.839553017, -0.739553017}

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