18x^2-21x-7=0

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Solution for 18x^2-21x-7=0 equation:


Simplifying
18x2 + -21x + -7 = 0

Reorder the terms:
-7 + -21x + 18x2 = 0

Solving
-7 + -21x + 18x2 = 0

Solving for variable 'x'.

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

Divide each side by '18'.
-0.3888888889 + -1.166666667x + x2 = 0

Move the constant term to the right:

Add '0.3888888889' to each side of the equation.
-0.3888888889 + -1.166666667x + 0.3888888889 + x2 = 0 + 0.3888888889

Reorder the terms:
-0.3888888889 + 0.3888888889 + -1.166666667x + x2 = 0 + 0.3888888889

Combine like terms: -0.3888888889 + 0.3888888889 = 0.0000000000
0.0000000000 + -1.166666667x + x2 = 0 + 0.3888888889
-1.166666667x + x2 = 0 + 0.3888888889

Combine like terms: 0 + 0.3888888889 = 0.3888888889
-1.166666667x + x2 = 0.3888888889

The x term is -1.166666667x.  Take half its coefficient (-0.5833333335).
Square it (0.3402777780) and add it to both sides.

Add '0.3402777780' to each side of the equation.
-1.166666667x + 0.3402777780 + x2 = 0.3888888889 + 0.3402777780

Reorder the terms:
0.3402777780 + -1.166666667x + x2 = 0.3888888889 + 0.3402777780

Combine like terms: 0.3888888889 + 0.3402777780 = 0.7291666669
0.3402777780 + -1.166666667x + x2 = 0.7291666669

Factor a perfect square on the left side:
(x + -0.5833333335)(x + -0.5833333335) = 0.7291666669

Calculate the square root of the right side: 0.853912564

Break this problem into two subproblems by setting 
(x + -0.5833333335) equal to 0.853912564 and -0.853912564.

Subproblem 1

x + -0.5833333335 = 0.853912564 Simplifying x + -0.5833333335 = 0.853912564 Reorder the terms: -0.5833333335 + x = 0.853912564 Solving -0.5833333335 + x = 0.853912564 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.5833333335' to each side of the equation. -0.5833333335 + 0.5833333335 + x = 0.853912564 + 0.5833333335 Combine like terms: -0.5833333335 + 0.5833333335 = 0.0000000000 0.0000000000 + x = 0.853912564 + 0.5833333335 x = 0.853912564 + 0.5833333335 Combine like terms: 0.853912564 + 0.5833333335 = 1.4372458975 x = 1.4372458975 Simplifying x = 1.4372458975

Subproblem 2

x + -0.5833333335 = -0.853912564 Simplifying x + -0.5833333335 = -0.853912564 Reorder the terms: -0.5833333335 + x = -0.853912564 Solving -0.5833333335 + x = -0.853912564 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.5833333335' to each side of the equation. -0.5833333335 + 0.5833333335 + x = -0.853912564 + 0.5833333335 Combine like terms: -0.5833333335 + 0.5833333335 = 0.0000000000 0.0000000000 + x = -0.853912564 + 0.5833333335 x = -0.853912564 + 0.5833333335 Combine like terms: -0.853912564 + 0.5833333335 = -0.2705792305 x = -0.2705792305 Simplifying x = -0.2705792305

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.4372458975, -0.2705792305}

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