x(-2x-15)=84

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Solution for x(-2x-15)=84 equation: 


Simplifying
x(-2x + -15) = 84

Reorder the terms:
x(-15 + -2x) = 84
(-15 * x + -2x * x) = 84
(-15x + -2x2) = 84

Solving
-15x + -2x2 = 84

Solving for variable 'x'.

Reorder the terms:
-84 + -15x + -2x2 = 84 + -84

Combine like terms: 84 + -84 = 0
-84 + -15x + -2x2 = 0

Factor out the Greatest Common Factor (GCF), '-1'.
-1(84 + 15x + 2x2) = 0

Ignore the factor -1.

Subproblem 1
Set the factor '(84 + 15x + 2x2)' equal to zero and attempt to solve:

Simplifying
84 + 15x + 2x2 = 0

Solving
84 + 15x + 2x2 = 0

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

Divide each side by '2'.
42 + 7.5x + x2 = 0

Move the constant term to the right:

Add '-42' to each side of the equation.
42 + 7.5x + -42 + x2 = 0 + -42

Reorder the terms:
42 + -42 + 7.5x + x2 = 0 + -42

Combine like terms: 42 + -42 = 0
0 + 7.5x + x2 = 0 + -42
7.5x + x2 = 0 + -42

Combine like terms: 0 + -42 = -42
7.5x + x2 = -42

The x term is 7.5x.  Take half its coefficient (3.75).
Square it (14.0625) and add it to both sides.

Add '14.0625' to each side of the equation.
7.5x + 14.0625 + x2 = -42 + 14.0625

Reorder the terms:
14.0625 + 7.5x + x2 = -42 + 14.0625

Combine like terms: -42 + 14.0625 = -27.9375
14.0625 + 7.5x + x2 = -27.9375

Factor a perfect square on the left side:
(x + 3.75)(x + 3.75) = -27.9375

Can't calculate square root of the right side.

The solution to this equation could not be determined.

This subproblem is being ignored because a solution could not be determined.

The solution to this equation could not be determined.

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