15x^2+x-1=0

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Solution for 15x^2+x-1=0 equation:


Simplifying
15x2 + x + -1 = 0

Reorder the terms:
-1 + x + 15x2 = 0

Solving
-1 + x + 15x2 = 0

Solving for variable 'x'.

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

Divide each side by '15'.
-0.06666666667 + 0.06666666667x + x2 = 0

Move the constant term to the right:

Add '0.06666666667' to each side of the equation.
-0.06666666667 + 0.06666666667x + 0.06666666667 + x2 = 0 + 0.06666666667

Reorder the terms:
-0.06666666667 + 0.06666666667 + 0.06666666667x + x2 = 0 + 0.06666666667

Combine like terms: -0.06666666667 + 0.06666666667 = 0.00000000000
0.00000000000 + 0.06666666667x + x2 = 0 + 0.06666666667
0.06666666667x + x2 = 0 + 0.06666666667

Combine like terms: 0 + 0.06666666667 = 0.06666666667
0.06666666667x + x2 = 0.06666666667

The x term is x.  Take half its coefficient (0.5).
Square it (0.25) and add it to both sides.

Add '0.25' to each side of the equation.
0.06666666667x + 0.25 + x2 = 0.06666666667 + 0.25

Reorder the terms:
0.25 + 0.06666666667x + x2 = 0.06666666667 + 0.25

Combine like terms: 0.06666666667 + 0.25 = 0.31666666667
0.25 + 0.06666666667x + x2 = 0.31666666667

Factor a perfect square on the left side:
(x + 0.5)(x + 0.5) = 0.31666666667

Calculate the square root of the right side: 0.562731434

Break this problem into two subproblems by setting 
(x + 0.5) equal to 0.562731434 and -0.562731434.

Subproblem 1

x + 0.5 = 0.562731434 Simplifying x + 0.5 = 0.562731434 Reorder the terms: 0.5 + x = 0.562731434 Solving 0.5 + x = 0.562731434 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = 0.562731434 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = 0.562731434 + -0.5 x = 0.562731434 + -0.5 Combine like terms: 0.562731434 + -0.5 = 0.062731434 x = 0.062731434 Simplifying x = 0.062731434

Subproblem 2

x + 0.5 = -0.562731434 Simplifying x + 0.5 = -0.562731434 Reorder the terms: 0.5 + x = -0.562731434 Solving 0.5 + x = -0.562731434 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.5' to each side of the equation. 0.5 + -0.5 + x = -0.562731434 + -0.5 Combine like terms: 0.5 + -0.5 = 0.0 0.0 + x = -0.562731434 + -0.5 x = -0.562731434 + -0.5 Combine like terms: -0.562731434 + -0.5 = -1.062731434 x = -1.062731434 Simplifying x = -1.062731434

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.062731434, -1.062731434}

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