3x^2+13x=18

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Solution for 3x^2+13x=18 equation:


Simplifying
3x2 + 13x = 18

Reorder the terms:
13x + 3x2 = 18

Solving
13x + 3x2 = 18

Solving for variable 'x'.

Reorder the terms:
-18 + 13x + 3x2 = 18 + -18

Combine like terms: 18 + -18 = 0
-18 + 13x + 3x2 = 0

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

Divide each side by '3'.
-6 + 4.333333333x + x2 = 0

Move the constant term to the right:

Add '6' to each side of the equation.
-6 + 4.333333333x + 6 + x2 = 0 + 6

Reorder the terms:
-6 + 6 + 4.333333333x + x2 = 0 + 6

Combine like terms: -6 + 6 = 0
0 + 4.333333333x + x2 = 0 + 6
4.333333333x + x2 = 0 + 6

Combine like terms: 0 + 6 = 6
4.333333333x + x2 = 6

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 = 6 + 4.694444446

Reorder the terms:
4.694444446 + 4.333333333x + x2 = 6 + 4.694444446

Combine like terms: 6 + 4.694444446 = 10.694444446
4.694444446 + 4.333333333x + x2 = 10.694444446

Factor a perfect square on the left side:
(x + 2.166666667)(x + 2.166666667) = 10.694444446

Calculate the square root of the right side: 3.270236145

Break this problem into two subproblems by setting 
(x + 2.166666667) equal to 3.270236145 and -3.270236145.

Subproblem 1

x + 2.166666667 = 3.270236145 Simplifying x + 2.166666667 = 3.270236145 Reorder the terms: 2.166666667 + x = 3.270236145 Solving 2.166666667 + x = 3.270236145 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 = 3.270236145 + -2.166666667 Combine like terms: 2.166666667 + -2.166666667 = 0.000000000 0.000000000 + x = 3.270236145 + -2.166666667 x = 3.270236145 + -2.166666667 Combine like terms: 3.270236145 + -2.166666667 = 1.103569478 x = 1.103569478 Simplifying x = 1.103569478

Subproblem 2

x + 2.166666667 = -3.270236145 Simplifying x + 2.166666667 = -3.270236145 Reorder the terms: 2.166666667 + x = -3.270236145 Solving 2.166666667 + x = -3.270236145 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 = -3.270236145 + -2.166666667 Combine like terms: 2.166666667 + -2.166666667 = 0.000000000 0.000000000 + x = -3.270236145 + -2.166666667 x = -3.270236145 + -2.166666667 Combine like terms: -3.270236145 + -2.166666667 = -5.436902812 x = -5.436902812 Simplifying x = -5.436902812

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.103569478, -5.436902812}

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