Substitute а = 6 into the expression:
9/(6-6^2) - 9/6= 9/(6-36) - 9/6= 9/(-30) - 9/6= -3/10 - 3/2= -3/10 - 15/10= -18/10= -9/5
Therefore, the value of the expression is -9/5 when a = 6.
Substitute а = 6 into the expression:
9/(6-6^2) - 9/6
= 9/(6-36) - 9/6
= 9/(-30) - 9/6
= -3/10 - 3/2
= -3/10 - 15/10
= -18/10
= -9/5
Therefore, the value of the expression is -9/5 when a = 6.