SAT Math 1.5 Algebra and Functions

Then we plug in the given functions here, so that's:

x squared minus 16 divided by x to the fourth minus 256.

The numerator and denominator both look like they're begging to be factored.

But let's start with the denominator ….because it has the larger exponent.

Hmmm, what does this ugly number factor into?

Well it kind of looks like a difference of two squares..

x to the fourth is a square of x squared...

And 256 is a perfect square of 16...

So we have x squared minus 16 times x squared plus 16.

Hey! The numerator just so happens to have (x2 - 16) as well.

Instead of factoring that equation even further, we can cancel both the numerator

and one of the factors in the denominator and arrive at 1 over x squared plus 16.

Answer's (A).