(7y^2+6y-9)-(2y^2-8y+8)=

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Solution for (7y^2+6y-9)-(2y^2-8y+8)= equation:


Simplifying
(7y2 + 6y + -9) + -1(2y2 + -8y + 8) = 0

Reorder the terms:
(-9 + 6y + 7y2) + -1(2y2 + -8y + 8) = 0

Remove parenthesis around (-9 + 6y + 7y2)
-9 + 6y + 7y2 + -1(2y2 + -8y + 8) = 0

Reorder the terms:
-9 + 6y + 7y2 + -1(8 + -8y + 2y2) = 0
-9 + 6y + 7y2 + (8 * -1 + -8y * -1 + 2y2 * -1) = 0
-9 + 6y + 7y2 + (-8 + 8y + -2y2) = 0

Reorder the terms:
-9 + -8 + 6y + 8y + 7y2 + -2y2 = 0

Combine like terms: -9 + -8 = -17
-17 + 6y + 8y + 7y2 + -2y2 = 0

Combine like terms: 6y + 8y = 14y
-17 + 14y + 7y2 + -2y2 = 0

Combine like terms: 7y2 + -2y2 = 5y2
-17 + 14y + 5y2 = 0

Solving
-17 + 14y + 5y2 = 0

Solving for variable 'y'.

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

Divide each side by '5'.
-3.4 + 2.8y + y2 = 0

Move the constant term to the right:

Add '3.4' to each side of the equation.
-3.4 + 2.8y + 3.4 + y2 = 0 + 3.4

Reorder the terms:
-3.4 + 3.4 + 2.8y + y2 = 0 + 3.4

Combine like terms: -3.4 + 3.4 = 0.0
0.0 + 2.8y + y2 = 0 + 3.4
2.8y + y2 = 0 + 3.4

Combine like terms: 0 + 3.4 = 3.4
2.8y + y2 = 3.4

The y term is 2.8y.  Take half its coefficient (1.4).
Square it (1.96) and add it to both sides.

Add '1.96' to each side of the equation.
2.8y + 1.96 + y2 = 3.4 + 1.96

Reorder the terms:
1.96 + 2.8y + y2 = 3.4 + 1.96

Combine like terms: 3.4 + 1.96 = 5.36
1.96 + 2.8y + y2 = 5.36

Factor a perfect square on the left side:
(y + 1.4)(y + 1.4) = 5.36

Calculate the square root of the right side: 2.315167381

Break this problem into two subproblems by setting 
(y + 1.4) equal to 2.315167381 and -2.315167381.

Subproblem 1

y + 1.4 = 2.315167381 Simplifying y + 1.4 = 2.315167381 Reorder the terms: 1.4 + y = 2.315167381 Solving 1.4 + y = 2.315167381 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-1.4' to each side of the equation. 1.4 + -1.4 + y = 2.315167381 + -1.4 Combine like terms: 1.4 + -1.4 = 0.0 0.0 + y = 2.315167381 + -1.4 y = 2.315167381 + -1.4 Combine like terms: 2.315167381 + -1.4 = 0.915167381 y = 0.915167381 Simplifying y = 0.915167381

Subproblem 2

y + 1.4 = -2.315167381 Simplifying y + 1.4 = -2.315167381 Reorder the terms: 1.4 + y = -2.315167381 Solving 1.4 + y = -2.315167381 Solving for variable 'y'. Move all terms containing y to the left, all other terms to the right. Add '-1.4' to each side of the equation. 1.4 + -1.4 + y = -2.315167381 + -1.4 Combine like terms: 1.4 + -1.4 = 0.0 0.0 + y = -2.315167381 + -1.4 y = -2.315167381 + -1.4 Combine like terms: -2.315167381 + -1.4 = -3.715167381 y = -3.715167381 Simplifying y = -3.715167381

Solution

The solution to the problem is based on the solutions from the subproblems. y = {0.915167381, -3.715167381}

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