f(x)=x2−x−42x2−36

It seems like you've made a mistake in your question. The function you've provided, "f(x)=x2−x−42x2−36", is not properly formatted.

If you're trying to express a rational function, it should look something like this: "f(x) = (x^2 - x - 42) / (x^2 - 36)".

If this is the function you're asking about, here's how you would simplify it:

Step 1: Factor the numerator and the denominator.

The numerator factors to (x - 7)(x + 6) and the denominator factors to (x - 6)(x + 6).

So, f(x) = (x - 7)(x + 6) / (x - 6)(x + 6).

Step 2: Cancel out the common factors.

The (x + 6) in the numerator and denominator cancel out, leaving you with f(x) = (x - 7) / (x - 6).

And that's your simplified function!