2a-3a-.5a^2=2.8

Solution for 2a-3a-.5a^2=2.8 equation:

Simplifying
2a + -3a + -0.5a2 = 2.8

Combine like terms: 2a + -3a = -1a
-1a + -0.5a2 = 2.8

Solving
-1a + -0.5a2 = 2.8

Solving for variable 'a'.

Reorder the terms:
-2.8 + -1a + -0.5a2 = 2.8 + -2.8

Combine like terms: 2.8 + -2.8 = 0.0
-2.8 + -1a + -0.5a2 = 0.0

Begin completing the square.  Divide all terms by
-0.5 the coefficient of the squared term: 

Divide each side by '-0.5'.
5.6 + 2a + a2 = 0

Move the constant term to the right:

Add '-5.6' to each side of the equation.
5.6 + 2a + -5.6 + a2 = 0 + -5.6

Reorder the terms:
5.6 + -5.6 + 2a + a2 = 0 + -5.6

Combine like terms: 5.6 + -5.6 = 0.0
0.0 + 2a + a2 = 0 + -5.6
2a + a2 = 0 + -5.6

Combine like terms: 0 + -5.6 = -5.6
2a + a2 = -5.6

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

Add '1' to each side of the equation.
2a + 1 + a2 = -5.6 + 1

Reorder the terms:
1 + 2a + a2 = -5.6 + 1

Combine like terms: -5.6 + 1 = -4.6
1 + 2a + a2 = -4.6

Factor a perfect square on the left side:
(a + 1)(a + 1) = -4.6

Can't calculate square root of the right side.

The solution to this equation could not be determined.