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

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

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

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

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

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

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

Solving
-25 + 16r2 = 0

Solving for variable 'r'.

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

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

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

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

Divide each side by '16'.
r2 = 1.5625

Simplifying
r2 = 1.5625

Take the square root of each side:
r = {-1.25, 1.25}