(x+15)(3x-17)=90

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Solution for (x+15)(3x-17)=90 equation:


Simplifying
(x + 15)(3x + -17) = 90

Reorder the terms:
(15 + x)(3x + -17) = 90

Reorder the terms:
(15 + x)(-17 + 3x) = 90

Multiply (15 + x) * (-17 + 3x)
(15(-17 + 3x) + x(-17 + 3x)) = 90
((-17 * 15 + 3x * 15) + x(-17 + 3x)) = 90
((-255 + 45x) + x(-17 + 3x)) = 90
(-255 + 45x + (-17 * x + 3x * x)) = 90
(-255 + 45x + (-17x + 3x2)) = 90

Combine like terms: 45x + -17x = 28x
(-255 + 28x + 3x2) = 90

Solving
-255 + 28x + 3x2 = 90

Solving for variable 'x'.

Reorder the terms:
-255 + -90 + 28x + 3x2 = 90 + -90

Combine like terms: -255 + -90 = -345
-345 + 28x + 3x2 = 90 + -90

Combine like terms: 90 + -90 = 0
-345 + 28x + 3x2 = 0

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

Divide each side by '3'.
-115 + 9.333333333x + x2 = 0

Move the constant term to the right:

Add '115' to each side of the equation.
-115 + 9.333333333x + 115 + x2 = 0 + 115

Reorder the terms:
-115 + 115 + 9.333333333x + x2 = 0 + 115

Combine like terms: -115 + 115 = 0
0 + 9.333333333x + x2 = 0 + 115
9.333333333x + x2 = 0 + 115

Combine like terms: 0 + 115 = 115
9.333333333x + x2 = 115

The x term is 9.333333333x.  Take half its coefficient (4.666666667).
Square it (21.77777778) and add it to both sides.

Add '21.77777778' to each side of the equation.
9.333333333x + 21.77777778 + x2 = 115 + 21.77777778

Reorder the terms:
21.77777778 + 9.333333333x + x2 = 115 + 21.77777778

Combine like terms: 115 + 21.77777778 = 136.77777778
21.77777778 + 9.333333333x + x2 = 136.77777778

Factor a perfect square on the left side:
(x + 4.666666667)(x + 4.666666667) = 136.77777778

Calculate the square root of the right side: 11.695203195

Break this problem into two subproblems by setting 
(x + 4.666666667) equal to 11.695203195 and -11.695203195.

Subproblem 1

x + 4.666666667 = 11.695203195 Simplifying x + 4.666666667 = 11.695203195 Reorder the terms: 4.666666667 + x = 11.695203195 Solving 4.666666667 + x = 11.695203195 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.666666667' to each side of the equation. 4.666666667 + -4.666666667 + x = 11.695203195 + -4.666666667 Combine like terms: 4.666666667 + -4.666666667 = 0.000000000 0.000000000 + x = 11.695203195 + -4.666666667 x = 11.695203195 + -4.666666667 Combine like terms: 11.695203195 + -4.666666667 = 7.028536528 x = 7.028536528 Simplifying x = 7.028536528

Subproblem 2

x + 4.666666667 = -11.695203195 Simplifying x + 4.666666667 = -11.695203195 Reorder the terms: 4.666666667 + x = -11.695203195 Solving 4.666666667 + x = -11.695203195 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.666666667' to each side of the equation. 4.666666667 + -4.666666667 + x = -11.695203195 + -4.666666667 Combine like terms: 4.666666667 + -4.666666667 = 0.000000000 0.000000000 + x = -11.695203195 + -4.666666667 x = -11.695203195 + -4.666666667 Combine like terms: -11.695203195 + -4.666666667 = -16.361869862 x = -16.361869862 Simplifying x = -16.361869862

Solution

The solution to the problem is based on the solutions from the subproblems. x = {7.028536528, -16.361869862}

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