hand i also have to explain the meaning of the answer
Instead of expecting us to show the entire solution and explain every step, you should be showing that you've made some effort to at least attempt this and have shown exactly where you are stuck. You should also have made some effort to post the question correctly and learn some LaTeX so that you can format it, instead of expecting us to decipher it.
To start, I expect you meant to find
Have you at least tried to evaluate , substitute these functions into the difference quotient and simplify?