-16(a-2)^2+81(3-a)^2
=-[[[4(a-2)]^2]-[9(3-a)]]^2]
=-[[4(a-2)+9(3-a)][4(a-2)-9(3-a)]]
=-[(4a-8+27-9a)(4a-8-27+9a)]
=-(19-5a)(13a-35)
-16(a-2)^2+81(3-a)^2
=-[[[4(a-2)]^2]-[9(3-a)]]^2]
=-[[4(a-2)+9(3-a)][4(a-2)-9(3-a)]]
=-[(4a-8+27-9a)(4a-8-27+9a)]
=-(19-5a)(13a-35)