(5r+4)(5r-4)=

Solution for (5r+4)(5r-4)= equation:

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

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

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

Multiply (4 + 5r) * (-4 + 5r)
(4(-4 + 5r) + 5r * (-4 + 5r)) = 0
((-4 * 4 + 5r * 4) + 5r * (-4 + 5r)) = 0
((-16 + 20r) + 5r * (-4 + 5r)) = 0
(-16 + 20r + (-4 * 5r + 5r * 5r)) = 0
(-16 + 20r + (-20r + 25r2)) = 0

Combine like terms: 20r + -20r = 0
(-16 + 0 + 25r2) = 0
(-16 + 25r2) = 0

Solving
-16 + 25r2 = 0

Solving for variable 'r'.

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

Add '16' to each side of the equation.
-16 + 16 + 25r2 = 0 + 16

Combine like terms: -16 + 16 = 0
0 + 25r2 = 0 + 16
25r2 = 0 + 16

Combine like terms: 0 + 16 = 16
25r2 = 16

Divide each side by '25'.
r2 = 0.64

Simplifying
r2 = 0.64

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