How do you find the x intercept of $f(x) = (x^2+9x)/(x^2+3x-4)$ ?

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Answer 1 · 2015-02-03T15:52:10

The $x$ -intercept is when $y=0$

So at first, you only have to look at the top half of the equation -- when this is $0$ the whole thing is $0$

Leaves us with $x^2+9x=0$

This can be re-written: $x^2+9x=x(x+9)=0$

So we have two answers:
$x=0 or (x+9)=0->x=-9$

Check the answers against the numerator (it may not be $0$ !)
$x=0->x^2+3x-4=-4$ which is OK
$x=-9->x^2+3x-4=50$ which is also $!=0$

How do you find the x intercept of f(x) = (x^2+9x)/(x^2+3x-4)f(x) = (x^2+9x)/(x^2+3x-4)?