0=7x^2-15x-7

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


Simplifying
0 = 7x2 + -15x + -7

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

Solving
0 = -7 + -15x + 7x2

Solving for variable 'x'.

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

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

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

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

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

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

Divide each side by '-7'.
-1 + -2.142857143x + x2 = 0

Move the constant term to the right:

Add '1' to each side of the equation.
-1 + -2.142857143x + 1 + x2 = 0 + 1

Reorder the terms:
-1 + 1 + -2.142857143x + x2 = 0 + 1

Combine like terms: -1 + 1 = 0
0 + -2.142857143x + x2 = 0 + 1
-2.142857143x + x2 = 0 + 1

Combine like terms: 0 + 1 = 1
-2.142857143x + x2 = 1

The x term is -2.142857143x.  Take half its coefficient (-1.071428572).
Square it (1.147959185) and add it to both sides.

Add '1.147959185' to each side of the equation.
-2.142857143x + 1.147959185 + x2 = 1 + 1.147959185

Reorder the terms:
1.147959185 + -2.142857143x + x2 = 1 + 1.147959185

Combine like terms: 1 + 1.147959185 = 2.147959185
1.147959185 + -2.142857143x + x2 = 2.147959185

Factor a perfect square on the left side:
(x + -1.071428572)(x + -1.071428572) = 2.147959185

Calculate the square root of the right side: 1.465591753

Break this problem into two subproblems by setting 
(x + -1.071428572) equal to 1.465591753 and -1.465591753.

Subproblem 1

x + -1.071428572 = 1.465591753 Simplifying x + -1.071428572 = 1.465591753 Reorder the terms: -1.071428572 + x = 1.465591753 Solving -1.071428572 + x = 1.465591753 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.071428572' to each side of the equation. -1.071428572 + 1.071428572 + x = 1.465591753 + 1.071428572 Combine like terms: -1.071428572 + 1.071428572 = 0.000000000 0.000000000 + x = 1.465591753 + 1.071428572 x = 1.465591753 + 1.071428572 Combine like terms: 1.465591753 + 1.071428572 = 2.537020325 x = 2.537020325 Simplifying x = 2.537020325

Subproblem 2

x + -1.071428572 = -1.465591753 Simplifying x + -1.071428572 = -1.465591753 Reorder the terms: -1.071428572 + x = -1.465591753 Solving -1.071428572 + x = -1.465591753 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.071428572' to each side of the equation. -1.071428572 + 1.071428572 + x = -1.465591753 + 1.071428572 Combine like terms: -1.071428572 + 1.071428572 = 0.000000000 0.000000000 + x = -1.465591753 + 1.071428572 x = -1.465591753 + 1.071428572 Combine like terms: -1.465591753 + 1.071428572 = -0.394163181 x = -0.394163181 Simplifying x = -0.394163181

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.537020325, -0.394163181}

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