The given expression represents the area. Find the side length of the square. 64r^2-144r+81

64r ^ 2-144r + 81
 For this case, what we can do is rewrite the second degree polynomial. 
 Apply resolvent:
 a = 64
 b = -144
 c = 81
 x = (- b +/- root (b ^ 2 - 4ac)) / 2a
 x = (- (- 144) +/- root ((- 144) ^ 2 - 4 * (64) * (81))) / 2 (64)
 x = (- (- 144) +/- root (0)) / 128
 x = 144/128
 x = 72/64
 x = 36/32
 x = 18/16
 x = 9/8
 Rewriting the polynomial:
 (8r-9) * (8r-9)
 Answer:
 The side length of the square is:
 (8r-9)