Question

5a(a+b+c)-5b(a-b-c)-5c(a+b-c)

Answer 1

5aa+5ab+5ac-5ba+5bb+5bc-5ca-5cb+5cc=
5aa+5bb+5cc=5(aa+bb+cc)

"aa"-это "а" в квадрате (во 2-й степени) и т.д.)

Answer 2

5a(a+b+c)-5b(a-b-c)-5c(a+b-c)=5а²+5ab+5ac-5ab+5b²+5bc-5ac-5bc+5c²=5a²+5b²+5c²=5(a²+b²+c²)