Can someone help explain how to do this equations!!

Question

anonymous · Answer

$$\frac{ x^2+9x+20 }{ x^2-25 }\div \frac{ x+4 }{ x-4 }$$

phi · Answer

dividing is the same as multiplying by the "inverse"
the inverse of a fraction is the fraction flipped:  inverse of a/b  is b/a
so flip the 2nd equation, and multiply

anonymous · Answer

multiply but it says to divide?

phi · Answer

Here is an example
$$4\div2 \text{ is the same as } 4\cdot \frac{1}{2}$$
flip and multiply

anonymous · Answer

k, i'll give it a try

phi · Answer

Also, for these problems FIRST always factor the polynomials (which you can for this problem)

phi · Answer

notice that the bottom is a difference of squares:
(a^2 - b^2)  factors to (a+b)(a-b)

anonymous · Answer

$$\frac{ x-4 }{ x-5 }$$
this is what i got. is it right?

anonymous · Answer

got it. thanks.

phi · Answer

Yes.  But if they want "excluded values",   (even if you canceled them away), add 
x≠ 5, x≠ -5, x≠ -4
(amended)