Question

решите плиз
2а (а+b-c)-2b(a-b-c)+2c(a-b+c)

Answer 1

2а (а+b-c)-2b(a-b-c)+2c(a-b+c) = 2ф^2 + 2ab - 2ac - 2ab + 2b^2 + 2bc + 2ac - 2bc + 2c^2 = 2(a^2+b^2+c^2)