3(x)(x)+7x=15

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Solution for 3(x)(x)+7x=15 equation:


Simplifying
3(x)(x) + 7x = 15

Multiply x * x
3x2 + 7x = 15

Reorder the terms:
7x + 3x2 = 15

Solving
7x + 3x2 = 15

Solving for variable 'x'.

Reorder the terms:
-15 + 7x + 3x2 = 15 + -15

Combine like terms: 15 + -15 = 0
-15 + 7x + 3x2 = 0

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

Divide each side by '3'.
-5 + 2.333333333x + x2 = 0

Move the constant term to the right:

Add '5' to each side of the equation.
-5 + 2.333333333x + 5 + x2 = 0 + 5

Reorder the terms:
-5 + 5 + 2.333333333x + x2 = 0 + 5

Combine like terms: -5 + 5 = 0
0 + 2.333333333x + x2 = 0 + 5
2.333333333x + x2 = 0 + 5

Combine like terms: 0 + 5 = 5
2.333333333x + x2 = 5

The x term is 2.333333333x.  Take half its coefficient (1.166666667).
Square it (1.361111112) and add it to both sides.

Add '1.361111112' to each side of the equation.
2.333333333x + 1.361111112 + x2 = 5 + 1.361111112

Reorder the terms:
1.361111112 + 2.333333333x + x2 = 5 + 1.361111112

Combine like terms: 5 + 1.361111112 = 6.361111112
1.361111112 + 2.333333333x + x2 = 6.361111112

Factor a perfect square on the left side:
(x + 1.166666667)(x + 1.166666667) = 6.361111112

Calculate the square root of the right side: 2.522124325

Break this problem into two subproblems by setting 
(x + 1.166666667) equal to 2.522124325 and -2.522124325.

Subproblem 1

x + 1.166666667 = 2.522124325 Simplifying x + 1.166666667 = 2.522124325 Reorder the terms: 1.166666667 + x = 2.522124325 Solving 1.166666667 + x = 2.522124325 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.166666667' to each side of the equation. 1.166666667 + -1.166666667 + x = 2.522124325 + -1.166666667 Combine like terms: 1.166666667 + -1.166666667 = 0.000000000 0.000000000 + x = 2.522124325 + -1.166666667 x = 2.522124325 + -1.166666667 Combine like terms: 2.522124325 + -1.166666667 = 1.355457658 x = 1.355457658 Simplifying x = 1.355457658

Subproblem 2

x + 1.166666667 = -2.522124325 Simplifying x + 1.166666667 = -2.522124325 Reorder the terms: 1.166666667 + x = -2.522124325 Solving 1.166666667 + x = -2.522124325 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1.166666667' to each side of the equation. 1.166666667 + -1.166666667 + x = -2.522124325 + -1.166666667 Combine like terms: 1.166666667 + -1.166666667 = 0.000000000 0.000000000 + x = -2.522124325 + -1.166666667 x = -2.522124325 + -1.166666667 Combine like terms: -2.522124325 + -1.166666667 = -3.688790992 x = -3.688790992 Simplifying x = -3.688790992

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.355457658, -3.688790992}

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