Question

81a ^{4} -16b ^{4} =

Answer 1

$81a^{4} -16b^{4} = (9a^{2}-4b^{2})(9a^{2}+4b^{2})=(3a-2b)(3a+2b)(9a^{2}+4b^{2})$

Answer 2

$81a ^{4} -16b ^{4} =(9a ^{2} -4b ^{2} )(9a ^{2} +4b ^{2} )=(9a ^{2} -4b ^{2} )(3a-2b)(3a+2b)$