(8y^2+5y-7)-(-5y^2+7y+2)+(9y^2-4y+2)=

Solution for (8y^2+5y-7)-(-5y^2+7y+2)+(9y^2-4y+2)= equation:

Simplifying
(8y2 + 5y + -7) + -1(-5y2 + 7y + 2) + (9y2 + -4y + 2) = 0

Reorder the terms:
(-7 + 5y + 8y2) + -1(-5y2 + 7y + 2) + (9y2 + -4y + 2) = 0

Remove parenthesis around (-7 + 5y + 8y2)
-7 + 5y + 8y2 + -1(-5y2 + 7y + 2) + (9y2 + -4y + 2) = 0

Reorder the terms:
-7 + 5y + 8y2 + -1(2 + 7y + -5y2) + (9y2 + -4y + 2) = 0
-7 + 5y + 8y2 + (2 * -1 + 7y * -1 + -5y2 * -1) + (9y2 + -4y + 2) = 0
-7 + 5y + 8y2 + (-2 + -7y + 5y2) + (9y2 + -4y + 2) = 0

Reorder the terms:
-7 + 5y + 8y2 + -2 + -7y + 5y2 + (2 + -4y + 9y2) = 0

Remove parenthesis around (2 + -4y + 9y2)
-7 + 5y + 8y2 + -2 + -7y + 5y2 + 2 + -4y + 9y2 = 0

Reorder the terms:
-7 + -2 + 2 + 5y + -7y + -4y + 8y2 + 5y2 + 9y2 = 0

Combine like terms: -7 + -2 = -9
-9 + 2 + 5y + -7y + -4y + 8y2 + 5y2 + 9y2 = 0

Combine like terms: -9 + 2 = -7
-7 + 5y + -7y + -4y + 8y2 + 5y2 + 9y2 = 0

Combine like terms: 5y + -7y = -2y
-7 + -2y + -4y + 8y2 + 5y2 + 9y2 = 0

Combine like terms: -2y + -4y = -6y
-7 + -6y + 8y2 + 5y2 + 9y2 = 0

Combine like terms: 8y2 + 5y2 = 13y2
-7 + -6y + 13y2 + 9y2 = 0

Combine like terms: 13y2 + 9y2 = 22y2
-7 + -6y + 22y2 = 0

Solving
-7 + -6y + 22y2 = 0

Solving for variable 'y'.

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

Divide each side by '22'.
-0.3181818182 + -0.2727272727y + y2 = 0

Move the constant term to the right:

Add '0.3181818182' to each side of the equation.
-0.3181818182 + -0.2727272727y + 0.3181818182 + y2 = 0 + 0.3181818182

Reorder the terms:
-0.3181818182 + 0.3181818182 + -0.2727272727y + y2 = 0 + 0.3181818182

Combine like terms: -0.3181818182 + 0.3181818182 = 0.0000000000
0.0000000000 + -0.2727272727y + y2 = 0 + 0.3181818182
-0.2727272727y + y2 = 0 + 0.3181818182

Combine like terms: 0 + 0.3181818182 = 0.3181818182
-0.2727272727y + y2 = 0.3181818182

The y term is -0.2727272727y.  Take half its coefficient (-0.1363636364).
Square it (0.01859504133) and add it to both sides.

Add '0.01859504133' to each side of the equation.
-0.2727272727y + 0.01859504133 + y2 = 0.3181818182 + 0.01859504133

Reorder the terms:
0.01859504133 + -0.2727272727y + y2 = 0.3181818182 + 0.01859504133

Combine like terms: 0.3181818182 + 0.01859504133 = 0.33677685953
0.01859504133 + -0.2727272727y + y2 = 0.33677685953

Factor a perfect square on the left side:
(y + -0.1363636364)(y + -0.1363636364) = 0.33677685953

Calculate the square root of the right side: 0.580324788

Break this problem into two subproblems by setting 
(y + -0.1363636364) equal to 0.580324788 and -0.580324788.

Subproblem 1
y + -0.1363636364 = 0.580324788

Simplifying
y + -0.1363636364 = 0.580324788

Reorder the terms:
-0.1363636364 + y = 0.580324788

Solving
-0.1363636364 + y = 0.580324788

Solving for variable 'y'.

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

Add '0.1363636364' to each side of the equation.
-0.1363636364 + 0.1363636364 + y = 0.580324788 + 0.1363636364

Combine like terms: -0.1363636364 + 0.1363636364 = 0.0000000000
0.0000000000 + y = 0.580324788 + 0.1363636364
y = 0.580324788 + 0.1363636364

Combine like terms: 0.580324788 + 0.1363636364 = 0.7166884244
y = 0.7166884244

Simplifying
y = 0.7166884244

Subproblem 2
y + -0.1363636364 = -0.580324788

Simplifying
y + -0.1363636364 = -0.580324788

Reorder the terms:
-0.1363636364 + y = -0.580324788

Solving
-0.1363636364 + y = -0.580324788

Solving for variable 'y'.

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

Add '0.1363636364' to each side of the equation.
-0.1363636364 + 0.1363636364 + y = -0.580324788 + 0.1363636364

Combine like terms: -0.1363636364 + 0.1363636364 = 0.0000000000
0.0000000000 + y = -0.580324788 + 0.1363636364
y = -0.580324788 + 0.1363636364

Combine like terms: -0.580324788 + 0.1363636364 = -0.4439611516
y = -0.4439611516

Simplifying
y = -0.4439611516

Solution
The solution to the problem is based on the solutions
from the subproblems.
y = {0.7166884244, -0.4439611516}