7x^2+15x+7=0

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


Simplifying
7x2 + 15x + 7 = 0

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

Solving
7 + 15x + 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'.
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 = 0.147959185
1.147959185 + 2.142857143x + x2 = 0.147959185

Factor a perfect square on the left side:
(x + 1.071428572)(x + 1.071428572) = 0.147959185

Calculate the square root of the right side: 0.384654631

Break this problem into two subproblems by setting 
(x + 1.071428572) equal to 0.384654631 and -0.384654631.

Subproblem 1

x + 1.071428572 = 0.384654631 Simplifying x + 1.071428572 = 0.384654631 Reorder the terms: 1.071428572 + x = 0.384654631 Solving 1.071428572 + x = 0.384654631 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 = 0.384654631 + -1.071428572 Combine like terms: 1.071428572 + -1.071428572 = 0.000000000 0.000000000 + x = 0.384654631 + -1.071428572 x = 0.384654631 + -1.071428572 Combine like terms: 0.384654631 + -1.071428572 = -0.686773941 x = -0.686773941 Simplifying x = -0.686773941

Subproblem 2

x + 1.071428572 = -0.384654631 Simplifying x + 1.071428572 = -0.384654631 Reorder the terms: 1.071428572 + x = -0.384654631 Solving 1.071428572 + x = -0.384654631 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 = -0.384654631 + -1.071428572 Combine like terms: 1.071428572 + -1.071428572 = 0.000000000 0.000000000 + x = -0.384654631 + -1.071428572 x = -0.384654631 + -1.071428572 Combine like terms: -0.384654631 + -1.071428572 = -1.456083203 x = -1.456083203 Simplifying x = -1.456083203

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-0.686773941, -1.456083203}

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