10x^2+2x-21=0

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


Simplifying
10x2 + 2x + -21 = 0

Reorder the terms:
-21 + 2x + 10x2 = 0

Solving
-21 + 2x + 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 + 0.2x + x2 = 0

Move the constant term to the right:

Add '2.1' to each side of the equation.
-2.1 + 0.2x + 2.1 + x2 = 0 + 2.1

Reorder the terms:
-2.1 + 2.1 + 0.2x + x2 = 0 + 2.1

Combine like terms: -2.1 + 2.1 = 0.0
0.0 + 0.2x + x2 = 0 + 2.1
0.2x + x2 = 0 + 2.1

Combine like terms: 0 + 2.1 = 2.1
0.2x + x2 = 2.1

The x term is 0.2x.  Take half its coefficient (0.1).
Square it (0.01) and add it to both sides.

Add '0.01' to each side of the equation.
0.2x + 0.01 + x2 = 2.1 + 0.01

Reorder the terms:
0.01 + 0.2x + x2 = 2.1 + 0.01

Combine like terms: 2.1 + 0.01 = 2.11
0.01 + 0.2x + x2 = 2.11

Factor a perfect square on the left side:
(x + 0.1)(x + 0.1) = 2.11

Calculate the square root of the right side: 1.452583905

Break this problem into two subproblems by setting 
(x + 0.1) equal to 1.452583905 and -1.452583905.

Subproblem 1

x + 0.1 = 1.452583905 Simplifying x + 0.1 = 1.452583905 Reorder the terms: 0.1 + x = 1.452583905 Solving 0.1 + x = 1.452583905 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1' to each side of the equation. 0.1 + -0.1 + x = 1.452583905 + -0.1 Combine like terms: 0.1 + -0.1 = 0.0 0.0 + x = 1.452583905 + -0.1 x = 1.452583905 + -0.1 Combine like terms: 1.452583905 + -0.1 = 1.352583905 x = 1.352583905 Simplifying x = 1.352583905

Subproblem 2

x + 0.1 = -1.452583905 Simplifying x + 0.1 = -1.452583905 Reorder the terms: 0.1 + x = -1.452583905 Solving 0.1 + x = -1.452583905 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1' to each side of the equation. 0.1 + -0.1 + x = -1.452583905 + -0.1 Combine like terms: 0.1 + -0.1 = 0.0 0.0 + x = -1.452583905 + -0.1 x = -1.452583905 + -0.1 Combine like terms: -1.452583905 + -0.1 = -1.552583905 x = -1.552583905 Simplifying x = -1.552583905

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.352583905, -1.552583905}

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