Answer:
The answer is 
.
Step-by-step explanation:
First, it is important to recall that the group law is not commutative in general, so we cannot assume it here. In order to solve the exercise we need to remember the axioms of group, specially the existence of the inverse element, i.e., for each element 
there exist another element, denoted by 
such that 
, where 
stands for the identity element of G.
So, given the equality 
we make a left multiplication by 
and we obtain:
But, 
. Hence, 
.
Now, in the equality we make a right multiplication by 
, and we obtain
.
Recall that 
and 
. Therefore,
.
The slope is -3.
Finding slope can be easy if you just remember that the formula is set up as y=mx+b.
The number in the 'm' place is always the slope.
Example: y=4x+1, the slope would be 4 because it's in the 'm' place.
If you have trouble remembering which place the slope is, trying thinking about skiing or sledding; you can only sled or ski down a Mountain slope. Mountain starts with M.
M=slope.
Hope this helps :)
If you have any questions, just let me know!
