(5u^2+9u-9)+(9u^2+4u+3)-(2u^2-8u-9)=

Solution for (5u^2+9u-9)+(9u^2+4u+3)-(2u^2-8u-9)= equation:

Simplifying
(5u2 + 9u + -9) + (9u2 + 4u + 3) + -1(2u2 + -8u + -9) = 0

Reorder the terms:
(-9 + 9u + 5u2) + (9u2 + 4u + 3) + -1(2u2 + -8u + -9) = 0

Remove parenthesis around (-9 + 9u + 5u2)
-9 + 9u + 5u2 + (9u2 + 4u + 3) + -1(2u2 + -8u + -9) = 0

Reorder the terms:
-9 + 9u + 5u2 + (3 + 4u + 9u2) + -1(2u2 + -8u + -9) = 0

Remove parenthesis around (3 + 4u + 9u2)
-9 + 9u + 5u2 + 3 + 4u + 9u2 + -1(2u2 + -8u + -9) = 0

Reorder the terms:
-9 + 9u + 5u2 + 3 + 4u + 9u2 + -1(-9 + -8u + 2u2) = 0
-9 + 9u + 5u2 + 3 + 4u + 9u2 + (-9 * -1 + -8u * -1 + 2u2 * -1) = 0
-9 + 9u + 5u2 + 3 + 4u + 9u2 + (9 + 8u + -2u2) = 0

Reorder the terms:
-9 + 3 + 9 + 9u + 4u + 8u + 5u2 + 9u2 + -2u2 = 0

Combine like terms: -9 + 3 = -6
-6 + 9 + 9u + 4u + 8u + 5u2 + 9u2 + -2u2 = 0

Combine like terms: -6 + 9 = 3
3 + 9u + 4u + 8u + 5u2 + 9u2 + -2u2 = 0

Combine like terms: 9u + 4u = 13u
3 + 13u + 8u + 5u2 + 9u2 + -2u2 = 0

Combine like terms: 13u + 8u = 21u
3 + 21u + 5u2 + 9u2 + -2u2 = 0

Combine like terms: 5u2 + 9u2 = 14u2
3 + 21u + 14u2 + -2u2 = 0

Combine like terms: 14u2 + -2u2 = 12u2
3 + 21u + 12u2 = 0

Solving
3 + 21u + 12u2 = 0

Solving for variable 'u'.

Factor out the Greatest Common Factor (GCF), '3'.
3(1 + 7u + 4u2) = 0

Ignore the factor 3.
Subproblem 1
Set the factor '(1 + 7u + 4u2)' equal to zero and attempt to solve:

Simplifying
1 + 7u + 4u2 = 0

Solving
1 + 7u + 4u2 = 0

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

Divide each side by '4'.
0.25 + 1.75u + u2 = 0

Move the constant term to the right:

Add '-0.25' to each side of the equation.
0.25 + 1.75u + -0.25 + u2 = 0 + -0.25

Reorder the terms:
0.25 + -0.25 + 1.75u + u2 = 0 + -0.25

Combine like terms: 0.25 + -0.25 = 0.00
0.00 + 1.75u + u2 = 0 + -0.25
1.75u + u2 = 0 + -0.25

Combine like terms: 0 + -0.25 = -0.25
1.75u + u2 = -0.25

The u term is 1.75u.  Take half its coefficient (0.875).
Square it (0.765625) and add it to both sides.

Add '0.765625' to each side of the equation.
1.75u + 0.765625 + u2 = -0.25 + 0.765625

Reorder the terms:
0.765625 + 1.75u + u2 = -0.25 + 0.765625

Combine like terms: -0.25 + 0.765625 = 0.515625
0.765625 + 1.75u + u2 = 0.515625

Factor a perfect square on the left side:
(u + 0.875)(u + 0.875) = 0.515625

Calculate the square root of the right side: 0.718070331

Break this problem into two subproblems by setting 
(u + 0.875) equal to 0.718070331 and -0.718070331.

Subproblem 1
u + 0.875 = 0.718070331

Simplifying
u + 0.875 = 0.718070331

Reorder the terms:
0.875 + u = 0.718070331

Solving
0.875 + u = 0.718070331

Solving for variable 'u'.

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

Add '-0.875' to each side of the equation.
0.875 + -0.875 + u = 0.718070331 + -0.875

Combine like terms: 0.875 + -0.875 = 0.000
0.000 + u = 0.718070331 + -0.875
u = 0.718070331 + -0.875

Combine like terms: 0.718070331 + -0.875 = -0.156929669
u = -0.156929669

Simplifying
u = -0.156929669

Subproblem 2
u + 0.875 = -0.718070331

Simplifying
u + 0.875 = -0.718070331

Reorder the terms:
0.875 + u = -0.718070331

Solving
0.875 + u = -0.718070331

Solving for variable 'u'.

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

Add '-0.875' to each side of the equation.
0.875 + -0.875 + u = -0.718070331 + -0.875

Combine like terms: 0.875 + -0.875 = 0.000
0.000 + u = -0.718070331 + -0.875
u = -0.718070331 + -0.875

Combine like terms: -0.718070331 + -0.875 = -1.593070331
u = -1.593070331

Simplifying
u = -1.593070331

Solution
The solution to the problem is based on the solutions
from the subproblems.
u = {-0.156929669, -1.593070331}
Solution
u = {-0.156929669, -1.593070331}