The other factor would be (x + 4). We can find this by using synthetic division. To do this, we must first find the divisor, which would be 9, if we let x - 9 equal to zero and solve for x. Then, for the dividend, we can use the coefficients and constant term values.
9| 1 -5 -36
9 36
1 4 0
Therefore, the other expression (x + 9) would be (x + 4). Hope this helped!