Question

Which is the value of 3b 2 −b 3b2-b when b = 5?

Answer 1

I think you mean 

3b^2 − b  ?

If so you just put in the 5 for b

3*(5)^2 - 5

Do the square first

5^2 = 25

3(25) - 5 =

75 - 5 = 

70.