4x^2+31x=42

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Solution for 4x^2+31x=42 equation:


Simplifying
4x2 + 31x = 42

Reorder the terms:
31x + 4x2 = 42

Solving
31x + 4x2 = 42

Solving for variable 'x'.

Reorder the terms:
-42 + 31x + 4x2 = 42 + -42

Combine like terms: 42 + -42 = 0
-42 + 31x + 4x2 = 0

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

Divide each side by '4'.
-10.5 + 7.75x + x2 = 0

Move the constant term to the right:

Add '10.5' to each side of the equation.
-10.5 + 7.75x + 10.5 + x2 = 0 + 10.5

Reorder the terms:
-10.5 + 10.5 + 7.75x + x2 = 0 + 10.5

Combine like terms: -10.5 + 10.5 = 0.0
0.0 + 7.75x + x2 = 0 + 10.5
7.75x + x2 = 0 + 10.5

Combine like terms: 0 + 10.5 = 10.5
7.75x + x2 = 10.5

The x term is 7.75x.  Take half its coefficient (3.875).
Square it (15.015625) and add it to both sides.

Add '15.015625' to each side of the equation.
7.75x + 15.015625 + x2 = 10.5 + 15.015625

Reorder the terms:
15.015625 + 7.75x + x2 = 10.5 + 15.015625

Combine like terms: 10.5 + 15.015625 = 25.515625
15.015625 + 7.75x + x2 = 25.515625

Factor a perfect square on the left side:
(x + 3.875)(x + 3.875) = 25.515625

Calculate the square root of the right side: 5.051299338

Break this problem into two subproblems by setting 
(x + 3.875) equal to 5.051299338 and -5.051299338.

Subproblem 1

x + 3.875 = 5.051299338 Simplifying x + 3.875 = 5.051299338 Reorder the terms: 3.875 + x = 5.051299338 Solving 3.875 + x = 5.051299338 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.875' to each side of the equation. 3.875 + -3.875 + x = 5.051299338 + -3.875 Combine like terms: 3.875 + -3.875 = 0.000 0.000 + x = 5.051299338 + -3.875 x = 5.051299338 + -3.875 Combine like terms: 5.051299338 + -3.875 = 1.176299338 x = 1.176299338 Simplifying x = 1.176299338

Subproblem 2

x + 3.875 = -5.051299338 Simplifying x + 3.875 = -5.051299338 Reorder the terms: 3.875 + x = -5.051299338 Solving 3.875 + x = -5.051299338 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3.875' to each side of the equation. 3.875 + -3.875 + x = -5.051299338 + -3.875 Combine like terms: 3.875 + -3.875 = 0.000 0.000 + x = -5.051299338 + -3.875 x = -5.051299338 + -3.875 Combine like terms: -5.051299338 + -3.875 = -8.926299338 x = -8.926299338 Simplifying x = -8.926299338

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.176299338, -8.926299338}

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