(a+12b)(a-12b)-(3a-2b)(-3a-2b)
=(a+12b)(a-12b)-(3a-2b)[-(3a+2b)]
=(a+12b)(a-12b)+(3a-2b)(3a+2b)
=a^2-144b^2+9a^2-4b^2
=11a^2-148b^2
(a+12b)(a-12b)-(3a-2b)(-3a-2b)
=(a+12b)(a-12b)-(3a-2b)[-(3a+2b)]
=(a+12b)(a-12b)+(3a-2b)(3a+2b)
=a^2-144b^2+9a^2-4b^2
=11a^2-148b^2