7x(x+8)-7+15=100

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Solution for 7x(x+8)-7+15=100 equation:


Simplifying
7x(x + 8) + -7 + 15 = 100

Reorder the terms:
7x(8 + x) + -7 + 15 = 100
(8 * 7x + x * 7x) + -7 + 15 = 100
(56x + 7x2) + -7 + 15 = 100

Reorder the terms:
-7 + 15 + 56x + 7x2 = 100

Combine like terms: -7 + 15 = 8
8 + 56x + 7x2 = 100

Solving
8 + 56x + 7x2 = 100

Solving for variable 'x'.

Reorder the terms:
8 + -100 + 56x + 7x2 = 100 + -100

Combine like terms: 8 + -100 = -92
-92 + 56x + 7x2 = 100 + -100

Combine like terms: 100 + -100 = 0
-92 + 56x + 7x2 = 0

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

Divide each side by '7'.
-13.14285714 + 8x + x2 = 0

Move the constant term to the right:

Add '13.14285714' to each side of the equation.
-13.14285714 + 8x + 13.14285714 + x2 = 0 + 13.14285714

Reorder the terms:
-13.14285714 + 13.14285714 + 8x + x2 = 0 + 13.14285714

Combine like terms: -13.14285714 + 13.14285714 = 0.00000000
0.00000000 + 8x + x2 = 0 + 13.14285714
8x + x2 = 0 + 13.14285714

Combine like terms: 0 + 13.14285714 = 13.14285714
8x + x2 = 13.14285714

The x term is 8x.  Take half its coefficient (4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
8x + 16 + x2 = 13.14285714 + 16

Reorder the terms:
16 + 8x + x2 = 13.14285714 + 16

Combine like terms: 13.14285714 + 16 = 29.14285714
16 + 8x + x2 = 29.14285714

Factor a perfect square on the left side:
(x + 4)(x + 4) = 29.14285714

Calculate the square root of the right side: 5.398412465

Break this problem into two subproblems by setting 
(x + 4) equal to 5.398412465 and -5.398412465.

Subproblem 1

x + 4 = 5.398412465 Simplifying x + 4 = 5.398412465 Reorder the terms: 4 + x = 5.398412465 Solving 4 + x = 5.398412465 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + x = 5.398412465 + -4 Combine like terms: 4 + -4 = 0 0 + x = 5.398412465 + -4 x = 5.398412465 + -4 Combine like terms: 5.398412465 + -4 = 1.398412465 x = 1.398412465 Simplifying x = 1.398412465

Subproblem 2

x + 4 = -5.398412465 Simplifying x + 4 = -5.398412465 Reorder the terms: 4 + x = -5.398412465 Solving 4 + x = -5.398412465 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4' to each side of the equation. 4 + -4 + x = -5.398412465 + -4 Combine like terms: 4 + -4 = 0 0 + x = -5.398412465 + -4 x = -5.398412465 + -4 Combine like terms: -5.398412465 + -4 = -9.398412465 x = -9.398412465 Simplifying x = -9.398412465

Solution

The solution to the problem is based on the solutions from the subproblems. x = {1.398412465, -9.398412465}

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