Select area between two bottom rows

I have data in Column A, and in Column B. I want to select the area from the bottom of column A to the bottom of column B (really, I want to delete that area). Here's the code I'm trying to use:

Firstrow = Range("A" & Rows.Count).End(xlUp).Row
    LastRow = Range("B" & Rows.Count).End(xlUp).Row
    Range(Firstrow:LastRow).Select

The last line has a syntax error, but I dont know how to resolve the syntax. Can someone help?