Find the derivative of the following functions (it is to be understand that a,b,c,d,p,q,r and s are fixed non-zero constants ):
`(a)/(x^(4))-(b)/(x^(2))+cosx`

Explanation

To find the derivative of the function \( y = \frac{a}{x^4} - \frac{b}{x^2} + \cos x \), we will follow these steps:

### Step 1: Rewrite the function
We can rewrite the function in terms of negative exponents:
\[ y = a x^{-4} - b x^{-2} + \cos x \]

...