Question

решите до 15 00 пж-та

Answer 1

(a+b)^2-(a-b)^2=(a+b+a-b)(a+b-a+b)=2a2b=4ab=0
(a+b)*c=ac+bc=|a||c|cos(ac)+|b||c|cos(bc)=|c|cos(bc)(|a|+|b|)=2*1/2(1+2)=3