7класс №1 (с-7)(с+7)= (7х-2)(7х+2)= (10р-6q)(10р+6q)= №2 (-a+b)(b-a)= (a+-b)= (-a--b)=

№1 
1) = с^2+7c-7c-49=c^2-49
2) = 49x^2+14x-14x-4=49x^2-4
3) = 100p^2+60pq-60pq-36q^2=100p^2-36q^2
№2
1) = -ab-a^2+b^2-ab=b^2-a^2-2ab
2) = -a^2-ab-ab+b^2=b^2-a^2-2ab
3) = a^2+ab+ab+b^2=a^2+b^2+2ab