Question

Which of the following is the graph of the rational function? y=x^2+2x-8/x^2-9

Answer 1

Notice that we can simplify both numerator and denominator of our rational function. In the numerator we have a quadratic expression of the form $ax^2+bx+c$. To to simplify it, we are going to find tow numbers that add to 2 and multiply to -8; those numbers are 4 and -2.
$x^2+2x-8=(x+4)(x-2)$
In the denominator we have a difference of squares:
$x^2-9=x^2-3^2=(x+3)(x-3)$

Now we can rewrite our function:
$y= \frac{x^2+2x-8}{x^2-9} = \frac{(x+4)(x-2)}{(x+3)(x-3)}$

From the simplified form of our rational function we can infer that its graph has two vertical asymptotes at $x=3$ and $x-3$

We can conclude that the graphic of our rational function is: