(x^2)+8x+15=-(7x)+21

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Solution for (x^2)+8x+15=-(7x)+21 equation:


Simplifying
(x2) + 8x + 15 = -1(7x) + 21
x2 + 8x + 15 = -1(7x) + 21

Reorder the terms:
15 + 8x + x2 = -1(7x) + 21

Remove parenthesis around (7x)
15 + 8x + x2 = -1 * 7x + 21

Multiply -1 * 7
15 + 8x + x2 = -7x + 21

Reorder the terms:
15 + 8x + x2 = 21 + -7x

Solving
15 + 8x + x2 = 21 + -7x

Solving for variable 'x'.

Reorder the terms:
15 + -21 + 8x + 7x + x2 = 21 + -7x + -21 + 7x

Combine like terms: 15 + -21 = -6
-6 + 8x + 7x + x2 = 21 + -7x + -21 + 7x

Combine like terms: 8x + 7x = 15x
-6 + 15x + x2 = 21 + -7x + -21 + 7x

Reorder the terms:
-6 + 15x + x2 = 21 + -21 + -7x + 7x

Combine like terms: 21 + -21 = 0
-6 + 15x + x2 = 0 + -7x + 7x
-6 + 15x + x2 = -7x + 7x

Combine like terms: -7x + 7x = 0
-6 + 15x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '6' to each side of the equation.
-6 + 15x + 6 + x2 = 0 + 6

Reorder the terms:
-6 + 6 + 15x + x2 = 0 + 6

Combine like terms: -6 + 6 = 0
0 + 15x + x2 = 0 + 6
15x + x2 = 0 + 6

Combine like terms: 0 + 6 = 6
15x + x2 = 6

The x term is 15x.  Take half its coefficient (7.5).
Square it (56.25) and add it to both sides.

Add '56.25' to each side of the equation.
15x + 56.25 + x2 = 6 + 56.25

Reorder the terms:
56.25 + 15x + x2 = 6 + 56.25

Combine like terms: 6 + 56.25 = 62.25
56.25 + 15x + x2 = 62.25

Factor a perfect square on the left side:
(x + 7.5)(x + 7.5) = 62.25

Calculate the square root of the right side: 7.889866919

Break this problem into two subproblems by setting 
(x + 7.5) equal to 7.889866919 and -7.889866919.

Subproblem 1

x + 7.5 = 7.889866919 Simplifying x + 7.5 = 7.889866919 Reorder the terms: 7.5 + x = 7.889866919 Solving 7.5 + x = 7.889866919 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-7.5' to each side of the equation. 7.5 + -7.5 + x = 7.889866919 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = 7.889866919 + -7.5 x = 7.889866919 + -7.5 Combine like terms: 7.889866919 + -7.5 = 0.389866919 x = 0.389866919 Simplifying x = 0.389866919

Subproblem 2

x + 7.5 = -7.889866919 Simplifying x + 7.5 = -7.889866919 Reorder the terms: 7.5 + x = -7.889866919 Solving 7.5 + x = -7.889866919 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-7.5' to each side of the equation. 7.5 + -7.5 + x = -7.889866919 + -7.5 Combine like terms: 7.5 + -7.5 = 0.0 0.0 + x = -7.889866919 + -7.5 x = -7.889866919 + -7.5 Combine like terms: -7.889866919 + -7.5 = -15.389866919 x = -15.389866919 Simplifying x = -15.389866919

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.389866919, -15.389866919}

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