I Have A 9yr Old Male Cat.He Has 3 Large Patches Of Clumped Fur.What Has Caused This?Should I Bring Him To The Vet.

Clumping of fur is called matting. This is more frequent problem of long haired cat but short haired cats also get this. The reasons are

1. Dirty fur
2. Dead fur
3. Skin Oils
4. Dust
5. Skin flakes

Over weight cats can not clean their fur and the result is Matt. Another possibility is arthritis due to which cat can nit clean fur. If the matts are tights then cut with scissor or groomer. Don't wet the fur. It will further tight them.
If the matts are loose then use talc free baby powder. After the matts are removed then brush daily by using comb.

Yes I would go to the vet it could be serious, and not just matted hair.