1. (y-4) * (y+4) - (y-3) ^2

2. (b-4) * (b+2) - (b-1) ^2

3. (a-2) * (a+4) - (a+1) ^2

4. (a-c) * (a+c) - c * (3a-c)

1. y^2+4y-4y-16 - (y^2-6y+9) = y^2+4y-4y-16-y^2+6y-9=-16+6-9=-19

2. b^2+2b-4b-8 - (b^2-2b+1) = b^2+2b-4b-8-b^2+2b-1=-9

3. a^2+4a-2a-8 - (a^2+2a+1) = a^2+4a-2a-8-a^2-2a-1=-9

4. a^2+ac-ac-c^2-3ac+c^2=a^2-3ac

вроде так