(7.2n^2-5n+2.5)+(4n^2+1.9n-2.8)=

Solution for (7.2n^2-5n+2.5)+(4n^2+1.9n-2.8)= equation:

Simplifying
(7.2n2 + -5n + 2.5) + (4n2 + 1.9n + -2.8) = 0

Reorder the terms:
(2.5 + -5n + 7.2n2) + (4n2 + 1.9n + -2.8) = 0

Remove parenthesis around (2.5 + -5n + 7.2n2)
2.5 + -5n + 7.2n2 + (4n2 + 1.9n + -2.8) = 0

Reorder the terms:
2.5 + -5n + 7.2n2 + (-2.8 + 1.9n + 4n2) = 0

Remove parenthesis around (-2.8 + 1.9n + 4n2)
2.5 + -5n + 7.2n2 + -2.8 + 1.9n + 4n2 = 0

Reorder the terms:
2.5 + -2.8 + -5n + 1.9n + 7.2n2 + 4n2 = 0

Combine like terms: 2.5 + -2.8 = -0.3
-0.3 + -5n + 1.9n + 7.2n2 + 4n2 = 0

Combine like terms: -5n + 1.9n = -3.1n
-0.3 + -3.1n + 7.2n2 + 4n2 = 0

Combine like terms: 7.2n2 + 4n2 = 11.2n2
-0.3 + -3.1n + 11.2n2 = 0

Solving
-0.3 + -3.1n + 11.2n2 = 0

Solving for variable 'n'.

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

Divide each side by '11.2'.
-0.02678571429 + -0.2767857143n + n2 = 0

Move the constant term to the right:

Add '0.02678571429' to each side of the equation.
-0.02678571429 + -0.2767857143n + 0.02678571429 + n2 = 0 + 0.02678571429

Reorder the terms:
-0.02678571429 + 0.02678571429 + -0.2767857143n + n2 = 0 + 0.02678571429

Combine like terms: -0.02678571429 + 0.02678571429 = 0.00000000000
0.00000000000 + -0.2767857143n + n2 = 0 + 0.02678571429
-0.2767857143n + n2 = 0 + 0.02678571429

Combine like terms: 0 + 0.02678571429 = 0.02678571429
-0.2767857143n + n2 = 0.02678571429

The n term is -0.2767857143n.  Take half its coefficient (-0.1383928572).
Square it (0.01915258292) and add it to both sides.

Add '0.01915258292' to each side of the equation.
-0.2767857143n + 0.01915258292 + n2 = 0.02678571429 + 0.01915258292

Reorder the terms:
0.01915258292 + -0.2767857143n + n2 = 0.02678571429 + 0.01915258292

Combine like terms: 0.02678571429 + 0.01915258292 = 0.04593829721
0.01915258292 + -0.2767857143n + n2 = 0.04593829721

Factor a perfect square on the left side:
(n + -0.1383928572)(n + -0.1383928572) = 0.04593829721

Calculate the square root of the right side: 0.214332212

Break this problem into two subproblems by setting 
(n + -0.1383928572) equal to 0.214332212 and -0.214332212.

Subproblem 1
n + -0.1383928572 = 0.214332212

Simplifying
n + -0.1383928572 = 0.214332212

Reorder the terms:
-0.1383928572 + n = 0.214332212

Solving
-0.1383928572 + n = 0.214332212

Solving for variable 'n'.

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

Add '0.1383928572' to each side of the equation.
-0.1383928572 + 0.1383928572 + n = 0.214332212 + 0.1383928572

Combine like terms: -0.1383928572 + 0.1383928572 = 0.0000000000
0.0000000000 + n = 0.214332212 + 0.1383928572
n = 0.214332212 + 0.1383928572

Combine like terms: 0.214332212 + 0.1383928572 = 0.3527250692
n = 0.3527250692

Simplifying
n = 0.3527250692

Subproblem 2
n + -0.1383928572 = -0.214332212

Simplifying
n + -0.1383928572 = -0.214332212

Reorder the terms:
-0.1383928572 + n = -0.214332212

Solving
-0.1383928572 + n = -0.214332212

Solving for variable 'n'.

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

Add '0.1383928572' to each side of the equation.
-0.1383928572 + 0.1383928572 + n = -0.214332212 + 0.1383928572

Combine like terms: -0.1383928572 + 0.1383928572 = 0.0000000000
0.0000000000 + n = -0.214332212 + 0.1383928572
n = -0.214332212 + 0.1383928572

Combine like terms: -0.214332212 + 0.1383928572 = -0.0759393548
n = -0.0759393548

Simplifying
n = -0.0759393548

Solution
The solution to the problem is based on the solutions
from the subproblems.
n = {0.3527250692, -0.0759393548}