Can someone help me with this problem... find all numbers that must be excluded from the domain of the rational expression.

x-9 / x2 + 4x - 45

Question

Can someone help me with this problem... find all numbers that must be excluded from the domain of the rational expression.

 x-9 / x2 + 4x - 45

anonymous · Answer

well, we want to avoid any x so that the denominator of this fraction is equal to 0, because we always want to avoid division by zero. So you have to exclude all x from the domain of this expression that satisfy x² + 4x - 45 = 0.

anonymous · Answer

I think I  have it...thanks!

anonymous · Answer

I got x ≠-5, x≠9

anonymous · Answer

hm seems like you messed up the signs a bit. It should be x ≠ 5, x ≠ -9 (try substituting them into the equation), alternatively look at (x-5) * (x+9) and it should be clear