7x^2+6x-15=0

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Solution for 7x^2+6x-15=0 equation:


Simplifying
7x2 + 6x + -15 = 0

Reorder the terms:
-15 + 6x + 7x2 = 0

Solving
-15 + 6x + 7x2 = 0

Solving for variable 'x'.

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

Divide each side by '7'.
-2.142857143 + 0.8571428571x + x2 = 0

Move the constant term to the right:

Add '2.142857143' to each side of the equation.
-2.142857143 + 0.8571428571x + 2.142857143 + x2 = 0 + 2.142857143

Reorder the terms:
-2.142857143 + 2.142857143 + 0.8571428571x + x2 = 0 + 2.142857143

Combine like terms: -2.142857143 + 2.142857143 = 0.000000000
0.000000000 + 0.8571428571x + x2 = 0 + 2.142857143
0.8571428571x + x2 = 0 + 2.142857143

Combine like terms: 0 + 2.142857143 = 2.142857143
0.8571428571x + x2 = 2.142857143

The x term is 0.8571428571x.  Take half its coefficient (0.4285714286).
Square it (0.1836734694) and add it to both sides.

Add '0.1836734694' to each side of the equation.
0.8571428571x + 0.1836734694 + x2 = 2.142857143 + 0.1836734694

Reorder the terms:
0.1836734694 + 0.8571428571x + x2 = 2.142857143 + 0.1836734694

Combine like terms: 2.142857143 + 0.1836734694 = 2.3265306124
0.1836734694 + 0.8571428571x + x2 = 2.3265306124

Factor a perfect square on the left side:
(x + 0.4285714286)(x + 0.4285714286) = 2.3265306124

Calculate the square root of the right side: 1.525296893

Break this problem into two subproblems by setting 
(x + 0.4285714286) equal to 1.525296893 and -1.525296893.

Subproblem 1

x + 0.4285714286 = 1.525296893 Simplifying x + 0.4285714286 = 1.525296893 Reorder the terms: 0.4285714286 + x = 1.525296893 Solving 0.4285714286 + x = 1.525296893 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.4285714286' to each side of the equation. 0.4285714286 + -0.4285714286 + x = 1.525296893 + -0.4285714286 Combine like terms: 0.4285714286 + -0.4285714286 = 0.0000000000 0.0000000000 + x = 1.525296893 + -0.4285714286 x = 1.525296893 + -0.4285714286 Combine like terms: 1.525296893 + -0.4285714286 = 1.0967254644 x = 1.0967254644 Simplifying x = 1.0967254644

Subproblem 2

x + 0.4285714286 = -1.525296893 Simplifying x + 0.4285714286 = -1.525296893 Reorder the terms: 0.4285714286 + x = -1.525296893 Solving 0.4285714286 + x = -1.525296893 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-0.4285714286' to each side of the equation. 0.4285714286 + -0.4285714286 + x = -1.525296893 + -0.4285714286 Combine like terms: 0.4285714286 + -0.4285714286 = 0.0000000000 0.0000000000 + x = -1.525296893 + -0.4285714286 x = -1.525296893 + -0.4285714286 Combine like terms: -1.525296893 + -0.4285714286 = -1.9538683216 x = -1.9538683216 Simplifying x = -1.9538683216

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.0967254644, -1.9538683216}

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