3y-2y(y+4)=8

Solution for 3y-2y(y+4)=8 equation:

Simplifying
3y + -2y(y + 4) = 8

Reorder the terms:
3y + -2y(4 + y) = 8
3y + (4 * -2y + y * -2y) = 8
3y + (-8y + -2y2) = 8

Combine like terms: 3y + -8y = -5y
-5y + -2y2 = 8

Solving
-5y + -2y2 = 8

Solving for variable 'y'.

Reorder the terms:
-8 + -5y + -2y2 = 8 + -8

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

Factor out the Greatest Common Factor (GCF), '-1'.
-1(8 + 5y + 2y2) = 0

Ignore the factor -1.
Subproblem 1
Set the factor '(8 + 5y + 2y2)' equal to zero and attempt to solve:

Simplifying
8 + 5y + 2y2 = 0

Solving
8 + 5y + 2y2 = 0

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

Divide each side by '2'.
4 + 2.5y + y2 = 0

Move the constant term to the right:

Add '-4' to each side of the equation.
4 + 2.5y + -4 + y2 = 0 + -4

Reorder the terms:
4 + -4 + 2.5y + y2 = 0 + -4

Combine like terms: 4 + -4 = 0
0 + 2.5y + y2 = 0 + -4
2.5y + y2 = 0 + -4

Combine like terms: 0 + -4 = -4
2.5y + y2 = -4

The y term is 2.5y.  Take half its coefficient (1.25).
Square it (1.5625) and add it to both sides.

Add '1.5625' to each side of the equation.
2.5y + 1.5625 + y2 = -4 + 1.5625

Reorder the terms:
1.5625 + 2.5y + y2 = -4 + 1.5625

Combine like terms: -4 + 1.5625 = -2.4375
1.5625 + 2.5y + y2 = -2.4375

Factor a perfect square on the left side:
(y + 1.25)(y + 1.25) = -2.4375

Can't calculate square root of the right side.

The solution to this equation could not be determined.

This subproblem is being ignored because a solution could not be determined.

The solution to this equation could not be determined.