Помогите,пож-та, 2 примера
1) (5а-3с)(5а+3с)-(7c-а)(7с+а)
2.) (4b+10c)(10c-4b)+(-5с+2b)(5c+2b)

СПАСИБО!!!!!!!!!!!!!!!!!!!!!

(5а-3с)(5а+3с)-(7c-а)(7с+а)=(5а)²-(3с)²- ((7c)²-(а)²)=25a²-9c²-49c²+a²== 26a²-58c²(4b+10c)(10c-4b)+(-5с+2b)(5c+2b)=(10c)²-(4b)²+((2b)²- (5с)²) = =100c²-16b²+4b²-25c²=75c²-12b²