>>11682769You know what a kernel is, right?
The kernel of a linear function f() is the set of all points x (a subspace) such that f(x) = 0.
Now why is E-1 a vector subspace?
Because for any u, Id(u) = u is true. Now you're looking for the subspace where f(u) = -u or where f+Id(u) = 0. That is the kernel of the function f+Id(). Similarly for E1.
