-5n^2-8n=4

Solution for -5n^2-8n=4 equation:

Simplifying
-5n2 + -8n = 4

Reorder the terms:
-8n + -5n2 = 4

Solving
-8n + -5n2 = 4

Solving for variable 'n'.

Reorder the terms:
-4 + -8n + -5n2 = 4 + -4

Combine like terms: 4 + -4 = 0
-4 + -8n + -5n2 = 0

Factor out the Greatest Common Factor (GCF), '-1'.
-1(4 + 8n + 5n2) = 0

Ignore the factor -1.
Subproblem 1
Set the factor '(4 + 8n + 5n2)' equal to zero and attempt to solve:

Simplifying
4 + 8n + 5n2 = 0

Solving
4 + 8n + 5n2 = 0

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

Divide each side by '5'.
0.8 + 1.6n + n2 = 0

Move the constant term to the right:

Add '-0.8' to each side of the equation.
0.8 + 1.6n + -0.8 + n2 = 0 + -0.8

Reorder the terms:
0.8 + -0.8 + 1.6n + n2 = 0 + -0.8

Combine like terms: 0.8 + -0.8 = 0.0
0.0 + 1.6n + n2 = 0 + -0.8
1.6n + n2 = 0 + -0.8

Combine like terms: 0 + -0.8 = -0.8
1.6n + n2 = -0.8

The n term is 1.6n.  Take half its coefficient (0.8).
Square it (0.64) and add it to both sides.

Add '0.64' to each side of the equation.
1.6n + 0.64 + n2 = -0.8 + 0.64

Reorder the terms:
0.64 + 1.6n + n2 = -0.8 + 0.64

Combine like terms: -0.8 + 0.64 = -0.16
0.64 + 1.6n + n2 = -0.16

Factor a perfect square on the left side:
(n + 0.8)(n + 0.8) = -0.16

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.