0.28v^2-0.36v-1.215=0

Solution for 0.28v^2-0.36v-1.215=0 equation:

Simplifying
0.28v2 + -0.36v + -1.215 = 0

Reorder the terms:
-1.215 + -0.36v + 0.28v2 = 0

Solving
-1.215 + -0.36v + 0.28v2 = 0

Solving for variable 'v'.

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

Divide each side by '0.28'.
-4.339285714 + -1.285714286v + v2 = 0

Move the constant term to the right:

Add '4.339285714' to each side of the equation.
-4.339285714 + -1.285714286v + 4.339285714 + v2 = 0 + 4.339285714

Reorder the terms:
-4.339285714 + 4.339285714 + -1.285714286v + v2 = 0 + 4.339285714

Combine like terms: -4.339285714 + 4.339285714 = 0.000000000
0.000000000 + -1.285714286v + v2 = 0 + 4.339285714
-1.285714286v + v2 = 0 + 4.339285714

Combine like terms: 0 + 4.339285714 = 4.339285714
-1.285714286v + v2 = 4.339285714

The v term is -1.285714286v.  Take half its coefficient (-0.642857143).
Square it (0.4132653063) and add it to both sides.

Add '0.4132653063' to each side of the equation.
-1.285714286v + 0.4132653063 + v2 = 4.339285714 + 0.4132653063

Reorder the terms:
0.4132653063 + -1.285714286v + v2 = 4.339285714 + 0.4132653063

Combine like terms: 4.339285714 + 0.4132653063 = 4.7525510203
0.4132653063 + -1.285714286v + v2 = 4.7525510203

Factor a perfect square on the left side:
(v + -0.642857143)(v + -0.642857143) = 4.7525510203

Calculate the square root of the right side: 2.180034637

Break this problem into two subproblems by setting 
(v + -0.642857143) equal to 2.180034637 and -2.180034637.

Subproblem 1
v + -0.642857143 = 2.180034637

Simplifying
v + -0.642857143 = 2.180034637

Reorder the terms:
-0.642857143 + v = 2.180034637

Solving
-0.642857143 + v = 2.180034637

Solving for variable 'v'.

Move all terms containing v to the left, all other terms to the right.

Add '0.642857143' to each side of the equation.
-0.642857143 + 0.642857143 + v = 2.180034637 + 0.642857143

Combine like terms: -0.642857143 + 0.642857143 = 0.000000000
0.000000000 + v = 2.180034637 + 0.642857143
v = 2.180034637 + 0.642857143

Combine like terms: 2.180034637 + 0.642857143 = 2.82289178
v = 2.82289178

Simplifying
v = 2.82289178

Subproblem 2
v + -0.642857143 = -2.180034637

Simplifying
v + -0.642857143 = -2.180034637

Reorder the terms:
-0.642857143 + v = -2.180034637

Solving
-0.642857143 + v = -2.180034637

Solving for variable 'v'.

Move all terms containing v to the left, all other terms to the right.

Add '0.642857143' to each side of the equation.
-0.642857143 + 0.642857143 + v = -2.180034637 + 0.642857143

Combine like terms: -0.642857143 + 0.642857143 = 0.000000000
0.000000000 + v = -2.180034637 + 0.642857143
v = -2.180034637 + 0.642857143

Combine like terms: -2.180034637 + 0.642857143 = -1.537177494
v = -1.537177494

Simplifying
v = -1.537177494

Solution
The solution to the problem is based on the solutions
from the subproblems.
v = {2.82289178, -1.537177494}