For F of X equal X ^2 + 3, we want to find F of t - 2. So every time we see our unknown X, we're going to stick in t - 2. So we're going to get the quantity t - 2 ^2 + 3. When we have t -, 2 ^2, we need to foil it out, so we get t ^2 - 4 T plus 4 + 3, or t ^2 - 4 T +7 for the F of A + H minus the F of A. I'd start by suggesting finding the F of A plus H first. So every time we see our X, we're going to stick in A + H, so we're going to have a plus H quantity squared +3, or a ^2 + 2 AH plus H ^2 + 3. Now F of A. Every time we see our X, we're going to stick in A, so we're going to get F of a equal a ^2 + 3. Now when we put those two together and we subtract them, we get the a ^2 + 2 AH plus H ^2 + 3 minus the quantity a ^2 + 3. Disturbing out the negative and combining like terms, we'd get 2AH plus H ^2. On the last part, we want F of A, so once again we stick A and every time we see an XA squared +3 and we want F of a -, H so we're going to stick in a -, H every time we see an X or the quantity a -, H ^2 + 3. Foiling that out, we get a ^2 -, 2 AH plus H ^2 + 3. So the F of A minus the F of a -, H we're going to distribute through the negative, combine our like terms and get 2AH minus H ^2.