4x^2+39x-42=0

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Solution for 4x^2+39x-42=0 equation:


Simplifying
4x2 + 39x + -42 = 0

Reorder the terms:
-42 + 39x + 4x2 = 0

Solving
-42 + 39x + 4x2 = 0

Solving for variable 'x'.

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

Divide each side by '4'.
-10.5 + 9.75x + x2 = 0

Move the constant term to the right:

Add '10.5' to each side of the equation.
-10.5 + 9.75x + 10.5 + x2 = 0 + 10.5

Reorder the terms:
-10.5 + 10.5 + 9.75x + x2 = 0 + 10.5

Combine like terms: -10.5 + 10.5 = 0.0
0.0 + 9.75x + x2 = 0 + 10.5
9.75x + x2 = 0 + 10.5

Combine like terms: 0 + 10.5 = 10.5
9.75x + x2 = 10.5

The x term is 9.75x.  Take half its coefficient (4.875).
Square it (23.765625) and add it to both sides.

Add '23.765625' to each side of the equation.
9.75x + 23.765625 + x2 = 10.5 + 23.765625

Reorder the terms:
23.765625 + 9.75x + x2 = 10.5 + 23.765625

Combine like terms: 10.5 + 23.765625 = 34.265625
23.765625 + 9.75x + x2 = 34.265625

Factor a perfect square on the left side:
(x + 4.875)(x + 4.875) = 34.265625

Calculate the square root of the right side: 5.853684737

Break this problem into two subproblems by setting 
(x + 4.875) equal to 5.853684737 and -5.853684737.

Subproblem 1

x + 4.875 = 5.853684737 Simplifying x + 4.875 = 5.853684737 Reorder the terms: 4.875 + x = 5.853684737 Solving 4.875 + x = 5.853684737 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.875' to each side of the equation. 4.875 + -4.875 + x = 5.853684737 + -4.875 Combine like terms: 4.875 + -4.875 = 0.000 0.000 + x = 5.853684737 + -4.875 x = 5.853684737 + -4.875 Combine like terms: 5.853684737 + -4.875 = 0.978684737 x = 0.978684737 Simplifying x = 0.978684737

Subproblem 2

x + 4.875 = -5.853684737 Simplifying x + 4.875 = -5.853684737 Reorder the terms: 4.875 + x = -5.853684737 Solving 4.875 + x = -5.853684737 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.875' to each side of the equation. 4.875 + -4.875 + x = -5.853684737 + -4.875 Combine like terms: 4.875 + -4.875 = 0.000 0.000 + x = -5.853684737 + -4.875 x = -5.853684737 + -4.875 Combine like terms: -5.853684737 + -4.875 = -10.728684737 x = -10.728684737 Simplifying x = -10.728684737

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.978684737, -10.728684737}

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