18x^2+7x-21=0

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


Simplifying
18x2 + 7x + -21 = 0

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

Solving
-21 + 7x + 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'.
-1.166666667 + 0.3888888889x + x2 = 0

Move the constant term to the right:

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

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

Combine like terms: -1.166666667 + 1.166666667 = 0.000000000
0.000000000 + 0.3888888889x + x2 = 0 + 1.166666667
0.3888888889x + x2 = 0 + 1.166666667

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

The x term is 0.3888888889x.  Take half its coefficient (0.1944444445).
Square it (0.03780864200) and add it to both sides.

Add '0.03780864200' to each side of the equation.
0.3888888889x + 0.03780864200 + x2 = 1.166666667 + 0.03780864200

Reorder the terms:
0.03780864200 + 0.3888888889x + x2 = 1.166666667 + 0.03780864200

Combine like terms: 1.166666667 + 0.03780864200 = 1.204475309
0.03780864200 + 0.3888888889x + x2 = 1.204475309

Factor a perfect square on the left side:
(x + 0.1944444445)(x + 0.1944444445) = 1.204475309

Calculate the square root of the right side: 1.097485904

Break this problem into two subproblems by setting 
(x + 0.1944444445) equal to 1.097485904 and -1.097485904.

Subproblem 1

x + 0.1944444445 = 1.097485904 Simplifying x + 0.1944444445 = 1.097485904 Reorder the terms: 0.1944444445 + x = 1.097485904 Solving 0.1944444445 + x = 1.097485904 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1944444445' to each side of the equation. 0.1944444445 + -0.1944444445 + x = 1.097485904 + -0.1944444445 Combine like terms: 0.1944444445 + -0.1944444445 = 0.0000000000 0.0000000000 + x = 1.097485904 + -0.1944444445 x = 1.097485904 + -0.1944444445 Combine like terms: 1.097485904 + -0.1944444445 = 0.9030414595 x = 0.9030414595 Simplifying x = 0.9030414595

Subproblem 2

x + 0.1944444445 = -1.097485904 Simplifying x + 0.1944444445 = -1.097485904 Reorder the terms: 0.1944444445 + x = -1.097485904 Solving 0.1944444445 + x = -1.097485904 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.1944444445' to each side of the equation. 0.1944444445 + -0.1944444445 + x = -1.097485904 + -0.1944444445 Combine like terms: 0.1944444445 + -0.1944444445 = 0.0000000000 0.0000000000 + x = -1.097485904 + -0.1944444445 x = -1.097485904 + -0.1944444445 Combine like terms: -1.097485904 + -0.1944444445 = -1.2919303485 x = -1.2919303485 Simplifying x = -1.2919303485

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.9030414595, -1.2919303485}

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