916=7x^2+84x+15

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Solution for 916=7x^2+84x+15 equation:


Simplifying
916 = 7x2 + 84x + 15

Reorder the terms:
916 = 15 + 84x + 7x2

Solving
916 = 15 + 84x + 7x2

Solving for variable 'x'.

Combine like terms: 916 + -15 = 901
901 + -84x + -7x2 = 15 + 84x + 7x2 + -15 + -84x + -7x2

Reorder the terms:
901 + -84x + -7x2 = 15 + -15 + 84x + -84x + 7x2 + -7x2

Combine like terms: 15 + -15 = 0
901 + -84x + -7x2 = 0 + 84x + -84x + 7x2 + -7x2
901 + -84x + -7x2 = 84x + -84x + 7x2 + -7x2

Combine like terms: 84x + -84x = 0
901 + -84x + -7x2 = 0 + 7x2 + -7x2
901 + -84x + -7x2 = 7x2 + -7x2

Combine like terms: 7x2 + -7x2 = 0
901 + -84x + -7x2 = 0

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

Divide each side by '-7'.
-128.7142857 + 12x + x2 = 0

Move the constant term to the right:

Add '128.7142857' to each side of the equation.
-128.7142857 + 12x + 128.7142857 + x2 = 0 + 128.7142857

Reorder the terms:
-128.7142857 + 128.7142857 + 12x + x2 = 0 + 128.7142857

Combine like terms: -128.7142857 + 128.7142857 = 0.0000000
0.0000000 + 12x + x2 = 0 + 128.7142857
12x + x2 = 0 + 128.7142857

Combine like terms: 0 + 128.7142857 = 128.7142857
12x + x2 = 128.7142857

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 = 128.7142857 + 36

Reorder the terms:
36 + 12x + x2 = 128.7142857 + 36

Combine like terms: 128.7142857 + 36 = 164.7142857
36 + 12x + x2 = 164.7142857

Factor a perfect square on the left side:
(x + 6)(x + 6) = 164.7142857

Calculate the square root of the right side: 12.834106346

Break this problem into two subproblems by setting 
(x + 6) equal to 12.834106346 and -12.834106346.

Subproblem 1

x + 6 = 12.834106346 Simplifying x + 6 = 12.834106346 Reorder the terms: 6 + x = 12.834106346 Solving 6 + x = 12.834106346 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 = 12.834106346 + -6 Combine like terms: 6 + -6 = 0 0 + x = 12.834106346 + -6 x = 12.834106346 + -6 Combine like terms: 12.834106346 + -6 = 6.834106346 x = 6.834106346 Simplifying x = 6.834106346

Subproblem 2

x + 6 = -12.834106346 Simplifying x + 6 = -12.834106346 Reorder the terms: 6 + x = -12.834106346 Solving 6 + x = -12.834106346 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 = -12.834106346 + -6 Combine like terms: 6 + -6 = 0 0 + x = -12.834106346 + -6 x = -12.834106346 + -6 Combine like terms: -12.834106346 + -6 = -18.834106346 x = -18.834106346 Simplifying x = -18.834106346

Solution

The solution to the problem is based on the solutions from the subproblems. x = {6.834106346, -18.834106346}

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