20x^2-11x-21=0

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Solution for 20x^2-11x-21=0 equation:


Simplifying
20x2 + -11x + -21 = 0

Reorder the terms:
-21 + -11x + 20x2 = 0

Solving
-21 + -11x + 20x2 = 0

Solving for variable 'x'.

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

Divide each side by '20'.
-1.05 + -0.55x + x2 = 0

Move the constant term to the right:

Add '1.05' to each side of the equation.
-1.05 + -0.55x + 1.05 + x2 = 0 + 1.05

Reorder the terms:
-1.05 + 1.05 + -0.55x + x2 = 0 + 1.05

Combine like terms: -1.05 + 1.05 = 0.00
0.00 + -0.55x + x2 = 0 + 1.05
-0.55x + x2 = 0 + 1.05

Combine like terms: 0 + 1.05 = 1.05
-0.55x + x2 = 1.05

The x term is -0.55x.  Take half its coefficient (-0.275).
Square it (0.075625) and add it to both sides.

Add '0.075625' to each side of the equation.
-0.55x + 0.075625 + x2 = 1.05 + 0.075625

Reorder the terms:
0.075625 + -0.55x + x2 = 1.05 + 0.075625

Combine like terms: 1.05 + 0.075625 = 1.125625
0.075625 + -0.55x + x2 = 1.125625

Factor a perfect square on the left side:
(x + -0.275)(x + -0.275) = 1.125625

Calculate the square root of the right side: 1.060954759

Break this problem into two subproblems by setting 
(x + -0.275) equal to 1.060954759 and -1.060954759.

Subproblem 1

x + -0.275 = 1.060954759 Simplifying x + -0.275 = 1.060954759 Reorder the terms: -0.275 + x = 1.060954759 Solving -0.275 + x = 1.060954759 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.275' to each side of the equation. -0.275 + 0.275 + x = 1.060954759 + 0.275 Combine like terms: -0.275 + 0.275 = 0.000 0.000 + x = 1.060954759 + 0.275 x = 1.060954759 + 0.275 Combine like terms: 1.060954759 + 0.275 = 1.335954759 x = 1.335954759 Simplifying x = 1.335954759

Subproblem 2

x + -0.275 = -1.060954759 Simplifying x + -0.275 = -1.060954759 Reorder the terms: -0.275 + x = -1.060954759 Solving -0.275 + x = -1.060954759 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.275' to each side of the equation. -0.275 + 0.275 + x = -1.060954759 + 0.275 Combine like terms: -0.275 + 0.275 = 0.000 0.000 + x = -1.060954759 + 0.275 x = -1.060954759 + 0.275 Combine like terms: -1.060954759 + 0.275 = -0.785954759 x = -0.785954759 Simplifying x = -0.785954759

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.335954759, -0.785954759}

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