3x^2-x-42=0

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Solution for 3x^2-x-42=0 equation:


Simplifying
3x2 + -1x + -42 = 0

Reorder the terms:
-42 + -1x + 3x2 = 0

Solving
-42 + -1x + 3x2 = 0

Solving for variable 'x'.

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

Divide each side by '3'.
-14 + -0.3333333333x + x2 = 0

Move the constant term to the right:

Add '14' to each side of the equation.
-14 + -0.3333333333x + 14 + x2 = 0 + 14

Reorder the terms:
-14 + 14 + -0.3333333333x + x2 = 0 + 14

Combine like terms: -14 + 14 = 0
0 + -0.3333333333x + x2 = 0 + 14
-0.3333333333x + x2 = 0 + 14

Combine like terms: 0 + 14 = 14
-0.3333333333x + x2 = 14

The x term is -0.3333333333x.  Take half its coefficient (-0.1666666667).
Square it (0.02777777779) and add it to both sides.

Add '0.02777777779' to each side of the equation.
-0.3333333333x + 0.02777777779 + x2 = 14 + 0.02777777779

Reorder the terms:
0.02777777779 + -0.3333333333x + x2 = 14 + 0.02777777779

Combine like terms: 14 + 0.02777777779 = 14.02777777779
0.02777777779 + -0.3333333333x + x2 = 14.02777777779

Factor a perfect square on the left side:
(x + -0.1666666667)(x + -0.1666666667) = 14.02777777779

Calculate the square root of the right side: 3.745367509

Break this problem into two subproblems by setting 
(x + -0.1666666667) equal to 3.745367509 and -3.745367509.

Subproblem 1

x + -0.1666666667 = 3.745367509 Simplifying x + -0.1666666667 = 3.745367509 Reorder the terms: -0.1666666667 + x = 3.745367509 Solving -0.1666666667 + x = 3.745367509 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.1666666667' to each side of the equation. -0.1666666667 + 0.1666666667 + x = 3.745367509 + 0.1666666667 Combine like terms: -0.1666666667 + 0.1666666667 = 0.0000000000 0.0000000000 + x = 3.745367509 + 0.1666666667 x = 3.745367509 + 0.1666666667 Combine like terms: 3.745367509 + 0.1666666667 = 3.9120341757 x = 3.9120341757 Simplifying x = 3.9120341757

Subproblem 2

x + -0.1666666667 = -3.745367509 Simplifying x + -0.1666666667 = -3.745367509 Reorder the terms: -0.1666666667 + x = -3.745367509 Solving -0.1666666667 + x = -3.745367509 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.1666666667' to each side of the equation. -0.1666666667 + 0.1666666667 + x = -3.745367509 + 0.1666666667 Combine like terms: -0.1666666667 + 0.1666666667 = 0.0000000000 0.0000000000 + x = -3.745367509 + 0.1666666667 x = -3.745367509 + 0.1666666667 Combine like terms: -3.745367509 + 0.1666666667 = -3.5787008423 x = -3.5787008423 Simplifying x = -3.5787008423

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.9120341757, -3.5787008423}

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