Since 81 - 16r^2 is a multiple of both 4 + r and 4 - r, it is automatically the LCM of this problem.
16r2+9r
LCM of 81 and 3 is 81.
The LCM is 162.
The LCM is 1539.
The LCM is 810.
The LCM is 1377.
The LCM is 2268.
The LCM of 6 and 81 is 162.
LCM of 81 and 375 is 10125.
The LCM of 81 and 216 is 648.
81
The LCM is 405.