Sum where Ax = Bx + Cx for the entire column A

Hello.

As the subject states I am trying to input a command where the Sum of Bx + Cx is displayed in Ax where X is the row number.

I understand I can manually enter A1 = B1 + C1 etc. This is an overly time consuming activity.

I would like to enter a single formula such that Ax = Bx + Cx where X = the row number between a range; for example between rows 8 and 150.

Thanks.