7x^2+142x-15=0

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Solution for 7x^2+142x-15=0 equation:


Simplifying
7x2 + 142x + -15 = 0

Reorder the terms:
-15 + 142x + 7x2 = 0

Solving
-15 + 142x + 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 + 20.28571429x + x2 = 0

Move the constant term to the right:

Add '2.142857143' to each side of the equation.
-2.142857143 + 20.28571429x + 2.142857143 + x2 = 0 + 2.142857143

Reorder the terms:
-2.142857143 + 2.142857143 + 20.28571429x + x2 = 0 + 2.142857143

Combine like terms: -2.142857143 + 2.142857143 = 0.000000000
0.000000000 + 20.28571429x + x2 = 0 + 2.142857143
20.28571429x + x2 = 0 + 2.142857143

Combine like terms: 0 + 2.142857143 = 2.142857143
20.28571429x + x2 = 2.142857143

The x term is 20.28571429x.  Take half its coefficient (10.14285715).
Square it (102.8775512) and add it to both sides.

Add '102.8775512' to each side of the equation.
20.28571429x + 102.8775512 + x2 = 2.142857143 + 102.8775512

Reorder the terms:
102.8775512 + 20.28571429x + x2 = 2.142857143 + 102.8775512

Combine like terms: 2.142857143 + 102.8775512 = 105.020408343
102.8775512 + 20.28571429x + x2 = 105.020408343

Factor a perfect square on the left side:
(x + 10.14285715)(x + 10.14285715) = 105.020408343

Calculate the square root of the right side: 10.247946543

Break this problem into two subproblems by setting 
(x + 10.14285715) equal to 10.247946543 and -10.247946543.

Subproblem 1

x + 10.14285715 = 10.247946543 Simplifying x + 10.14285715 = 10.247946543 Reorder the terms: 10.14285715 + x = 10.247946543 Solving 10.14285715 + x = 10.247946543 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-10.14285715' to each side of the equation. 10.14285715 + -10.14285715 + x = 10.247946543 + -10.14285715 Combine like terms: 10.14285715 + -10.14285715 = 0.00000000 0.00000000 + x = 10.247946543 + -10.14285715 x = 10.247946543 + -10.14285715 Combine like terms: 10.247946543 + -10.14285715 = 0.105089393 x = 0.105089393 Simplifying x = 0.105089393

Subproblem 2

x + 10.14285715 = -10.247946543 Simplifying x + 10.14285715 = -10.247946543 Reorder the terms: 10.14285715 + x = -10.247946543 Solving 10.14285715 + x = -10.247946543 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-10.14285715' to each side of the equation. 10.14285715 + -10.14285715 + x = -10.247946543 + -10.14285715 Combine like terms: 10.14285715 + -10.14285715 = 0.00000000 0.00000000 + x = -10.247946543 + -10.14285715 x = -10.247946543 + -10.14285715 Combine like terms: -10.247946543 + -10.14285715 = -20.390803693 x = -20.390803693 Simplifying x = -20.390803693

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.105089393, -20.390803693}

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