7x^2+84x-720=0

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Solution for 7x^2+84x-720=0 equation:


Simplifying
7x2 + 84x + -720 = 0

Reorder the terms:
-720 + 84x + 7x2 = 0

Solving
-720 + 84x + 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'.
-102.8571429 + 12x + x2 = 0

Move the constant term to the right:

Add '102.8571429' to each side of the equation.
-102.8571429 + 12x + 102.8571429 + x2 = 0 + 102.8571429

Reorder the terms:
-102.8571429 + 102.8571429 + 12x + x2 = 0 + 102.8571429

Combine like terms: -102.8571429 + 102.8571429 = 0.0000000
0.0000000 + 12x + x2 = 0 + 102.8571429
12x + x2 = 0 + 102.8571429

Combine like terms: 0 + 102.8571429 = 102.8571429
12x + x2 = 102.8571429

The x term is 12x.  Take half its coefficient (6).
Square it (36) and add it to both sides.

Add '36' to each side of the equation.
12x + 36 + x2 = 102.8571429 + 36

Reorder the terms:
36 + 12x + x2 = 102.8571429 + 36

Combine like terms: 102.8571429 + 36 = 138.8571429
36 + 12x + x2 = 138.8571429

Factor a perfect square on the left side:
(x + 6)(x + 6) = 138.8571429

Calculate the square root of the right side: 11.783766075

Break this problem into two subproblems by setting 
(x + 6) equal to 11.783766075 and -11.783766075.

Subproblem 1

x + 6 = 11.783766075 Simplifying x + 6 = 11.783766075 Reorder the terms: 6 + x = 11.783766075 Solving 6 + x = 11.783766075 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-6' to each side of the equation. 6 + -6 + x = 11.783766075 + -6 Combine like terms: 6 + -6 = 0 0 + x = 11.783766075 + -6 x = 11.783766075 + -6 Combine like terms: 11.783766075 + -6 = 5.783766075 x = 5.783766075 Simplifying x = 5.783766075

Subproblem 2

x + 6 = -11.783766075 Simplifying x + 6 = -11.783766075 Reorder the terms: 6 + x = -11.783766075 Solving 6 + x = -11.783766075 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-6' to each side of the equation. 6 + -6 + x = -11.783766075 + -6 Combine like terms: 6 + -6 = 0 0 + x = -11.783766075 + -6 x = -11.783766075 + -6 Combine like terms: -11.783766075 + -6 = -17.783766075 x = -17.783766075 Simplifying x = -17.783766075

Solution

The solution to the problem is based on the solutions from the subproblems. x = {5.783766075, -17.783766075}

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