0.1=0.04-0.05n(n+2)

Solution for 0.1=0.04-0.05n(n+2) equation:

Simplifying
0.1 = 0.04 + -0.05n(n + 2)

Reorder the terms:
0.1 = 0.04 + -0.05n(2 + n)
0.1 = 0.04 + (2 * -0.05n + n * -0.05n)
0.1 = 0.04 + (-0.1n + -0.05n2)

Solving
0.1 = 0.04 + -0.1n + -0.05n2

Solving for variable 'n'.

Combine like terms: 0.1 + -0.04 = 0.06
0.06 + 0.1n + 0.05n2 = 0.04 + -0.1n + -0.05n2 + -0.04 + 0.1n + 0.05n2

Reorder the terms:
0.06 + 0.1n + 0.05n2 = 0.04 + -0.04 + -0.1n + 0.1n + -0.05n2 + 0.05n2

Combine like terms: 0.04 + -0.04 = 0.00
0.06 + 0.1n + 0.05n2 = 0.00 + -0.1n + 0.1n + -0.05n2 + 0.05n2
0.06 + 0.1n + 0.05n2 = -0.1n + 0.1n + -0.05n2 + 0.05n2

Combine like terms: -0.1n + 0.1n = 0.0
0.06 + 0.1n + 0.05n2 = 0.0 + -0.05n2 + 0.05n2
0.06 + 0.1n + 0.05n2 = -0.05n2 + 0.05n2

Combine like terms: -0.05n2 + 0.05n2 = 0.00
0.06 + 0.1n + 0.05n2 = 0.00

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

Divide each side by '0.05'.
1.2 + 2n + n2 = 0

Move the constant term to the right:

Add '-1.2' to each side of the equation.
1.2 + 2n + -1.2 + n2 = 0 + -1.2

Reorder the terms:
1.2 + -1.2 + 2n + n2 = 0 + -1.2

Combine like terms: 1.2 + -1.2 = 0.0
0.0 + 2n + n2 = 0 + -1.2
2n + n2 = 0 + -1.2

Combine like terms: 0 + -1.2 = -1.2
2n + n2 = -1.2

The n term is 2n.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2n + 1 + n2 = -1.2 + 1

Reorder the terms:
1 + 2n + n2 = -1.2 + 1

Combine like terms: -1.2 + 1 = -0.2
1 + 2n + n2 = -0.2

Factor a perfect square on the left side:
(n + 1)(n + 1) = -0.2

Can't calculate square root of the right side.

The solution to this equation could not be determined.