Can you go backwards with your method?

What is the value of the expression i 0 × i 1 × i 2 × i 3 × i 4? 1 –1 i –i

Two numbers have a sum of -19. one number is x. what expression represents the other number?

One cell phone plan charges $20 per month plus $0.15 per minute used. a second cell phone plan charges $35 per month plus $0.10 per minute used. write and solve an equation to find the number of minutes you must talk to have the same cost for both calling plans.