Let S and T be linear transformations from a finite dimensional vector...
To show that S and T are both nilpotent, we need to show that there exists a positive integer n such that S^n = 0 and T^n = 0.
Since S(T(v)) = 0 for all v, this means that the image of T is contained in the null space of S. Let's denote the null space of S as N(S).
Now, consider the image of T applied to itself: T(T(v)). Since the image of T is contained in N(S), this means that T(T(v)) is also in N(S).
Similarly, we can consider T(T(T(v))), which is in N(S) since the image of T is contained in N(S).
We can continue this process, and for any positive integer k, we have T^k(v) in N(S).
Since V is a finite dimensional vector space, this process must eventually terminate. Let k = dim(V)+1. Then, we have T^(dim(V)+1)(v) = 0 for all v in V.
Therefore, T^(dim(V)+1) = 0, which means that T is nilpotent.
Similarly, we can show that S is nilpotent. Since S(T(v)) = 0 for all v, this means that the image of T is contained in the null space of S.
Again, we can consider S(S(v)) and continue this process. Since V is finite dimensional, this process must eventually terminate. Let k = dim(V)+1. Then, we have S^(dim(V)+1)(v) = 0 for all v in V.
Therefore, S^(dim(V)+1) = 0, which means that S is nilpotent.
Therefore, both S and T are nilpotent linear transformations.