Question

[nguyễn vũ phương linh]

cho \(\left|a^{\rightarrow}\right|\)= 3, \(\left|b^{\rightarrow}\right|\)= 2 ( \(a^{\rightarrow}\), \(b^{\rightarrow}\)) = 120 độ.

tính \(a^{\rightarrow}\).\(b^{\rightarrow}\), (\(a^{\rightarrow}\)+\(b^{\rightarrow}\)); (\(a^{\rightarrow}\)- \(b^{\rightarrow}\)); (\(a^{\rightarrow}\)+2\(b^{\rightarrow}\)).(2\(a^{\rightarrow}\)- \(b^{\rightarrow}\))