21x^2-18x-20=0

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Solution for 21x^2-18x-20=0 equation:


Simplifying
21x2 + -18x + -20 = 0

Reorder the terms:
-20 + -18x + 21x2 = 0

Solving
-20 + -18x + 21x2 = 0

Solving for variable 'x'.

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

Divide each side by '21'.
-0.9523809524 + -0.8571428571x + x2 = 0

Move the constant term to the right:

Add '0.9523809524' to each side of the equation.
-0.9523809524 + -0.8571428571x + 0.9523809524 + x2 = 0 + 0.9523809524

Reorder the terms:
-0.9523809524 + 0.9523809524 + -0.8571428571x + x2 = 0 + 0.9523809524

Combine like terms: -0.9523809524 + 0.9523809524 = 0.0000000000
0.0000000000 + -0.8571428571x + x2 = 0 + 0.9523809524
-0.8571428571x + x2 = 0 + 0.9523809524

Combine like terms: 0 + 0.9523809524 = 0.9523809524
-0.8571428571x + x2 = 0.9523809524

The x term is -0.8571428571x.  Take half its coefficient (-0.4285714286).
Square it (0.1836734694) and add it to both sides.

Add '0.1836734694' to each side of the equation.
-0.8571428571x + 0.1836734694 + x2 = 0.9523809524 + 0.1836734694

Reorder the terms:
0.1836734694 + -0.8571428571x + x2 = 0.9523809524 + 0.1836734694

Combine like terms: 0.9523809524 + 0.1836734694 = 1.1360544218
0.1836734694 + -0.8571428571x + x2 = 1.1360544218

Factor a perfect square on the left side:
(x + -0.4285714286)(x + -0.4285714286) = 1.1360544218

Calculate the square root of the right side: 1.065858537

Break this problem into two subproblems by setting 
(x + -0.4285714286) equal to 1.065858537 and -1.065858537.

Subproblem 1

x + -0.4285714286 = 1.065858537 Simplifying x + -0.4285714286 = 1.065858537 Reorder the terms: -0.4285714286 + x = 1.065858537 Solving -0.4285714286 + x = 1.065858537 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4285714286' to each side of the equation. -0.4285714286 + 0.4285714286 + x = 1.065858537 + 0.4285714286 Combine like terms: -0.4285714286 + 0.4285714286 = 0.0000000000 0.0000000000 + x = 1.065858537 + 0.4285714286 x = 1.065858537 + 0.4285714286 Combine like terms: 1.065858537 + 0.4285714286 = 1.4944299656 x = 1.4944299656 Simplifying x = 1.4944299656

Subproblem 2

x + -0.4285714286 = -1.065858537 Simplifying x + -0.4285714286 = -1.065858537 Reorder the terms: -0.4285714286 + x = -1.065858537 Solving -0.4285714286 + x = -1.065858537 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.4285714286' to each side of the equation. -0.4285714286 + 0.4285714286 + x = -1.065858537 + 0.4285714286 Combine like terms: -0.4285714286 + 0.4285714286 = 0.0000000000 0.0000000000 + x = -1.065858537 + 0.4285714286 x = -1.065858537 + 0.4285714286 Combine like terms: -1.065858537 + 0.4285714286 = -0.6372871084 x = -0.6372871084 Simplifying x = -0.6372871084

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.4944299656, -0.6372871084}

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