(5x-8)(3x+20)=138

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Solution for (5x-8)(3x+20)=138 equation:


Simplifying
(5x + -8)(3x + 20) = 138

Reorder the terms:
(-8 + 5x)(3x + 20) = 138

Reorder the terms:
(-8 + 5x)(20 + 3x) = 138

Multiply (-8 + 5x) * (20 + 3x)
(-8(20 + 3x) + 5x * (20 + 3x)) = 138
((20 * -8 + 3x * -8) + 5x * (20 + 3x)) = 138
((-160 + -24x) + 5x * (20 + 3x)) = 138
(-160 + -24x + (20 * 5x + 3x * 5x)) = 138
(-160 + -24x + (100x + 15x2)) = 138

Combine like terms: -24x + 100x = 76x
(-160 + 76x + 15x2) = 138

Solving
-160 + 76x + 15x2 = 138

Solving for variable 'x'.

Reorder the terms:
-160 + -138 + 76x + 15x2 = 138 + -138

Combine like terms: -160 + -138 = -298
-298 + 76x + 15x2 = 138 + -138

Combine like terms: 138 + -138 = 0
-298 + 76x + 15x2 = 0

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

Divide each side by '15'.
-19.86666667 + 5.066666667x + x2 = 0

Move the constant term to the right:

Add '19.86666667' to each side of the equation.
-19.86666667 + 5.066666667x + 19.86666667 + x2 = 0 + 19.86666667

Reorder the terms:
-19.86666667 + 19.86666667 + 5.066666667x + x2 = 0 + 19.86666667

Combine like terms: -19.86666667 + 19.86666667 = 0.00000000
0.00000000 + 5.066666667x + x2 = 0 + 19.86666667
5.066666667x + x2 = 0 + 19.86666667

Combine like terms: 0 + 19.86666667 = 19.86666667
5.066666667x + x2 = 19.86666667

The x term is 5.066666667x.  Take half its coefficient (2.533333334).
Square it (6.417777781) and add it to both sides.

Add '6.417777781' to each side of the equation.
5.066666667x + 6.417777781 + x2 = 19.86666667 + 6.417777781

Reorder the terms:
6.417777781 + 5.066666667x + x2 = 19.86666667 + 6.417777781

Combine like terms: 19.86666667 + 6.417777781 = 26.284444451
6.417777781 + 5.066666667x + x2 = 26.284444451

Factor a perfect square on the left side:
(x + 2.533333334)(x + 2.533333334) = 26.284444451

Calculate the square root of the right side: 5.126835715

Break this problem into two subproblems by setting 
(x + 2.533333334) equal to 5.126835715 and -5.126835715.

Subproblem 1

x + 2.533333334 = 5.126835715 Simplifying x + 2.533333334 = 5.126835715 Reorder the terms: 2.533333334 + x = 5.126835715 Solving 2.533333334 + x = 5.126835715 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.533333334' to each side of the equation. 2.533333334 + -2.533333334 + x = 5.126835715 + -2.533333334 Combine like terms: 2.533333334 + -2.533333334 = 0.000000000 0.000000000 + x = 5.126835715 + -2.533333334 x = 5.126835715 + -2.533333334 Combine like terms: 5.126835715 + -2.533333334 = 2.593502381 x = 2.593502381 Simplifying x = 2.593502381

Subproblem 2

x + 2.533333334 = -5.126835715 Simplifying x + 2.533333334 = -5.126835715 Reorder the terms: 2.533333334 + x = -5.126835715 Solving 2.533333334 + x = -5.126835715 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.533333334' to each side of the equation. 2.533333334 + -2.533333334 + x = -5.126835715 + -2.533333334 Combine like terms: 2.533333334 + -2.533333334 = 0.000000000 0.000000000 + x = -5.126835715 + -2.533333334 x = -5.126835715 + -2.533333334 Combine like terms: -5.126835715 + -2.533333334 = -7.660169049 x = -7.660169049 Simplifying x = -7.660169049

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.593502381, -7.660169049}

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