a) (c-9) (c+9) — (c+4) (c-4)=б) (7c+2) (7c-2) — (7c-5) (7c+5)=в)

a) (c-9) (c+9) — (c+4) (c-4)=c^2+9c-9c-81-c^2+4c-4c+16=-65 б) (7c+2) (7c-2) — (7c-5) (7c+5)=49c^2-14c+14c-4-49c^2-35c+35c+25=21 в) (3c+1) (1-3c)+(3c-8) (8+3c)=3c-9c^2+1-3c+24c+9c^2-64-24c=-63 г) (0,3c+1,1) (1,1-0,3c)+(0,3c-0,2) (0,2+0,3c)=0,33c-0,09c^2+1,21-0,33c+0,06c+0,09c^2-0,04-0,06c=1,17