In order to simplify this fraction we need to find greatest common factor of 17 and 34.
Let us first find all possible factors of 17 and 34.
factors of 17 are 1 and 17 (since 17 is a prime number)
factors of 34 are 1, 2, 17 and 34.
common factor of 17 and 34 is 17
so we divide both numerator and denominator by 17.
dividing -17 by 17, we have -1
dividing 34 by 17 we have 2

So our answer is -1/2