(x+1)(3x+1)=90

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Solution for (x+1)(3x+1)=90 equation:


Simplifying
(x + 1)(3x + 1) = 90

Reorder the terms:
(1 + x)(3x + 1) = 90

Reorder the terms:
(1 + x)(1 + 3x) = 90

Multiply (1 + x) * (1 + 3x)
(1(1 + 3x) + x(1 + 3x)) = 90
((1 * 1 + 3x * 1) + x(1 + 3x)) = 90
((1 + 3x) + x(1 + 3x)) = 90
(1 + 3x + (1 * x + 3x * x)) = 90
(1 + 3x + (1x + 3x2)) = 90

Combine like terms: 3x + 1x = 4x
(1 + 4x + 3x2) = 90

Solving
1 + 4x + 3x2 = 90

Solving for variable 'x'.

Reorder the terms:
1 + -90 + 4x + 3x2 = 90 + -90

Combine like terms: 1 + -90 = -89
-89 + 4x + 3x2 = 90 + -90

Combine like terms: 90 + -90 = 0
-89 + 4x + 3x2 = 0

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

Divide each side by '3'.
-29.66666667 + 1.333333333x + x2 = 0

Move the constant term to the right:

Add '29.66666667' to each side of the equation.
-29.66666667 + 1.333333333x + 29.66666667 + x2 = 0 + 29.66666667

Reorder the terms:
-29.66666667 + 29.66666667 + 1.333333333x + x2 = 0 + 29.66666667

Combine like terms: -29.66666667 + 29.66666667 = 0.00000000
0.00000000 + 1.333333333x + x2 = 0 + 29.66666667
1.333333333x + x2 = 0 + 29.66666667

Combine like terms: 0 + 29.66666667 = 29.66666667
1.333333333x + x2 = 29.66666667

The x term is 1.333333333x.  Take half its coefficient (0.6666666665).
Square it (0.4444444442) and add it to both sides.

Add '0.4444444442' to each side of the equation.
1.333333333x + 0.4444444442 + x2 = 29.66666667 + 0.4444444442

Reorder the terms:
0.4444444442 + 1.333333333x + x2 = 29.66666667 + 0.4444444442

Combine like terms: 29.66666667 + 0.4444444442 = 30.1111111142
0.4444444442 + 1.333333333x + x2 = 30.1111111142

Factor a perfect square on the left side:
(x + 0.6666666665)(x + 0.6666666665) = 30.1111111142

Calculate the square root of the right side: 5.487359211

Break this problem into two subproblems by setting 
(x + 0.6666666665) equal to 5.487359211 and -5.487359211.

Subproblem 1

x + 0.6666666665 = 5.487359211 Simplifying x + 0.6666666665 = 5.487359211 Reorder the terms: 0.6666666665 + x = 5.487359211 Solving 0.6666666665 + x = 5.487359211 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.6666666665' to each side of the equation. 0.6666666665 + -0.6666666665 + x = 5.487359211 + -0.6666666665 Combine like terms: 0.6666666665 + -0.6666666665 = 0.0000000000 0.0000000000 + x = 5.487359211 + -0.6666666665 x = 5.487359211 + -0.6666666665 Combine like terms: 5.487359211 + -0.6666666665 = 4.8206925445 x = 4.8206925445 Simplifying x = 4.8206925445

Subproblem 2

x + 0.6666666665 = -5.487359211 Simplifying x + 0.6666666665 = -5.487359211 Reorder the terms: 0.6666666665 + x = -5.487359211 Solving 0.6666666665 + x = -5.487359211 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.6666666665' to each side of the equation. 0.6666666665 + -0.6666666665 + x = -5.487359211 + -0.6666666665 Combine like terms: 0.6666666665 + -0.6666666665 = 0.0000000000 0.0000000000 + x = -5.487359211 + -0.6666666665 x = -5.487359211 + -0.6666666665 Combine like terms: -5.487359211 + -0.6666666665 = -6.1540258775 x = -6.1540258775 Simplifying x = -6.1540258775

Solution

The solution to the problem is based on the solutions from the subproblems. x = {4.8206925445, -6.1540258775}

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