My math class has just started getting into calculus and I have a few questions that I'd like to ask. Our school uses a program called TLM that spits out some random math problems from a huge database, and here are a couple of questions that I'm having trouble with.

Given the function $\displaystyle f(x) = 4x^2-1x+4$

evaluate $\displaystyle f(2+\Delta x)$

For this question should I just pop in $\displaystyle 2+\Delta x$ for x?

EDIT:

$\displaystyle y=5x^2+6x+21 $

The question then asks me what is $\displaystyle \Delta Y$ and $\displaystyle \Delta y / \Delta x$ when x changes from 1.6 to 2.2

For delta y I just subbed in the numbers and got 15

For finding the dy/dx I'm drawing a complete blank. I feel like it should be easy but I can't figure out what to do.