3x(x+5)-2(x+2)=20

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Solution for 3x(x+5)-2(x+2)=20 equation:


Simplifying
3x(x + 5) + -2(x + 2) = 20

Reorder the terms:
3x(5 + x) + -2(x + 2) = 20
(5 * 3x + x * 3x) + -2(x + 2) = 20
(15x + 3x2) + -2(x + 2) = 20

Reorder the terms:
15x + 3x2 + -2(2 + x) = 20
15x + 3x2 + (2 * -2 + x * -2) = 20
15x + 3x2 + (-4 + -2x) = 20

Reorder the terms:
-4 + 15x + -2x + 3x2 = 20

Combine like terms: 15x + -2x = 13x
-4 + 13x + 3x2 = 20

Solving
-4 + 13x + 3x2 = 20

Solving for variable 'x'.

Reorder the terms:
-4 + -20 + 13x + 3x2 = 20 + -20

Combine like terms: -4 + -20 = -24
-24 + 13x + 3x2 = 20 + -20

Combine like terms: 20 + -20 = 0
-24 + 13x + 3x2 = 0

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

Divide each side by '3'.
-8 + 4.333333333x + x2 = 0

Move the constant term to the right:

Add '8' to each side of the equation.
-8 + 4.333333333x + 8 + x2 = 0 + 8

Reorder the terms:
-8 + 8 + 4.333333333x + x2 = 0 + 8

Combine like terms: -8 + 8 = 0
0 + 4.333333333x + x2 = 0 + 8
4.333333333x + x2 = 0 + 8

Combine like terms: 0 + 8 = 8
4.333333333x + x2 = 8

The x term is 4.333333333x.  Take half its coefficient (2.166666667).
Square it (4.694444446) and add it to both sides.

Add '4.694444446' to each side of the equation.
4.333333333x + 4.694444446 + x2 = 8 + 4.694444446

Reorder the terms:
4.694444446 + 4.333333333x + x2 = 8 + 4.694444446

Combine like terms: 8 + 4.694444446 = 12.694444446
4.694444446 + 4.333333333x + x2 = 12.694444446

Factor a perfect square on the left side:
(x + 2.166666667)(x + 2.166666667) = 12.694444446

Calculate the square root of the right side: 3.562926388

Break this problem into two subproblems by setting 
(x + 2.166666667) equal to 3.562926388 and -3.562926388.

Subproblem 1

x + 2.166666667 = 3.562926388 Simplifying x + 2.166666667 = 3.562926388 Reorder the terms: 2.166666667 + x = 3.562926388 Solving 2.166666667 + x = 3.562926388 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.166666667' to each side of the equation. 2.166666667 + -2.166666667 + x = 3.562926388 + -2.166666667 Combine like terms: 2.166666667 + -2.166666667 = 0.000000000 0.000000000 + x = 3.562926388 + -2.166666667 x = 3.562926388 + -2.166666667 Combine like terms: 3.562926388 + -2.166666667 = 1.396259721 x = 1.396259721 Simplifying x = 1.396259721

Subproblem 2

x + 2.166666667 = -3.562926388 Simplifying x + 2.166666667 = -3.562926388 Reorder the terms: 2.166666667 + x = -3.562926388 Solving 2.166666667 + x = -3.562926388 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.166666667' to each side of the equation. 2.166666667 + -2.166666667 + x = -3.562926388 + -2.166666667 Combine like terms: 2.166666667 + -2.166666667 = 0.000000000 0.000000000 + x = -3.562926388 + -2.166666667 x = -3.562926388 + -2.166666667 Combine like terms: -3.562926388 + -2.166666667 = -5.729593055 x = -5.729593055 Simplifying x = -5.729593055

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.396259721, -5.729593055}

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