Trong không gian R2, cho tích vô hướng (x, y)=((x1;x2),(y1;y2))=x1y1−x1y2−x2y1 +3x2y2. Tính độ dài của véctơ v=(−1;3)

Abank manager wants to encourage new customers to open accounts with principals of at least $2 comma 500. he decides to make a poster advertising a simple interest rate of 3%. what must the principal be if the bank manager also wants to advertise that one can earn $10 the first month? can the poster correctly say, "open an account of $2 comma 500 and earn at least $10 interest in 1 month! "?