1) (a-4)(a+4) -2a(3-a) =a² -16 -6a +2a² =3a² -6a -16
2) (a-8)(a-7) -(a-9)² =a² -7a -8a +56 -(a² -18a +81) =a² -15a +56 -a² +18a -81 =3a -25
3) (b+3)(b-3) +(2b+3)² =b² -9 + 4b² +12b +9 =5b² +12b
4) 3(x-5)² +10x -8x² =3(x² -10x +25) +10x -8x² =3x² -30x +75 +10x -8x² =75 -20x -5x²