(5y+4)(5y-4)=0

Solution for (5y+4)(5y-4)=0 equation:

Simplifying
(5y + 4)(5y + -4) = 0

Reorder the terms:
(4 + 5y)(5y + -4) = 0

Reorder the terms:
(4 + 5y)(-4 + 5y) = 0

Multiply (4 + 5y) * (-4 + 5y)
(4(-4 + 5y) + 5y * (-4 + 5y)) = 0
((-4 * 4 + 5y * 4) + 5y * (-4 + 5y)) = 0
((-16 + 20y) + 5y * (-4 + 5y)) = 0
(-16 + 20y + (-4 * 5y + 5y * 5y)) = 0
(-16 + 20y + (-20y + 25y2)) = 0

Combine like terms: 20y + -20y = 0
(-16 + 0 + 25y2) = 0
(-16 + 25y2) = 0

Solving
-16 + 25y2 = 0

Solving for variable 'y'.

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

Add '16' to each side of the equation.
-16 + 16 + 25y2 = 0 + 16

Combine like terms: -16 + 16 = 0
0 + 25y2 = 0 + 16
25y2 = 0 + 16

Combine like terms: 0 + 16 = 16
25y2 = 16

Divide each side by '25'.
y2 = 0.64

Simplifying
y2 = 0.64

Take the square root of each side:
y = {-0.8, 0.8}