10x^2+28x-21=0

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Solution for 10x^2+28x-21=0 equation:


Simplifying
10x2 + 28x + -21 = 0

Reorder the terms:
-21 + 28x + 10x2 = 0

Solving
-21 + 28x + 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 + 2.8x + x2 = 0

Move the constant term to the right:

Add '2.1' to each side of the equation.
-2.1 + 2.8x + 2.1 + x2 = 0 + 2.1

Reorder the terms:
-2.1 + 2.1 + 2.8x + x2 = 0 + 2.1

Combine like terms: -2.1 + 2.1 = 0.0
0.0 + 2.8x + x2 = 0 + 2.1
2.8x + x2 = 0 + 2.1

Combine like terms: 0 + 2.1 = 2.1
2.8x + x2 = 2.1

The x term is 2.8x.  Take half its coefficient (1.4).
Square it (1.96) and add it to both sides.

Add '1.96' to each side of the equation.
2.8x + 1.96 + x2 = 2.1 + 1.96

Reorder the terms:
1.96 + 2.8x + x2 = 2.1 + 1.96

Combine like terms: 2.1 + 1.96 = 4.06
1.96 + 2.8x + x2 = 4.06

Factor a perfect square on the left side:
(x + 1.4)(x + 1.4) = 4.06

Calculate the square root of the right side: 2.014944168

Break this problem into two subproblems by setting 
(x + 1.4) equal to 2.014944168 and -2.014944168.

Subproblem 1

x + 1.4 = 2.014944168 Simplifying x + 1.4 = 2.014944168 Reorder the terms: 1.4 + x = 2.014944168 Solving 1.4 + x = 2.014944168 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.4' to each side of the equation. 1.4 + -1.4 + x = 2.014944168 + -1.4 Combine like terms: 1.4 + -1.4 = 0.0 0.0 + x = 2.014944168 + -1.4 x = 2.014944168 + -1.4 Combine like terms: 2.014944168 + -1.4 = 0.614944168 x = 0.614944168 Simplifying x = 0.614944168

Subproblem 2

x + 1.4 = -2.014944168 Simplifying x + 1.4 = -2.014944168 Reorder the terms: 1.4 + x = -2.014944168 Solving 1.4 + x = -2.014944168 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.4' to each side of the equation. 1.4 + -1.4 + x = -2.014944168 + -1.4 Combine like terms: 1.4 + -1.4 = 0.0 0.0 + x = -2.014944168 + -1.4 x = -2.014944168 + -1.4 Combine like terms: -2.014944168 + -1.4 = -3.414944168 x = -3.414944168 Simplifying x = -3.414944168

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.614944168, -3.414944168}

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