What is the equation of the line

Based on what i know about mean, this doesn't add up.

You are making a battery for a science project. you have copper wire for your first electrode. you need to choose a conductor, a second electrode, and a device to plug into your battery. you have already chosen a lemon conductor. complete each statement below about the options that include a lemon conductor.

What is the 12th term of b(n)=-4-2(n-1)