I'm trying to teach myself math for physics (a middle aged physicist wannabee). Wikipedia's proof for the exisitence of a JC form for matrix A in Cn,n states: "The range of A − λ I, denoted by , is an invariant subspace of A" I'm having trouble seeing why any element of Ran(A − λ I) is in the range also of A. Also, where can I find instructions on putting equations in this forum? Thankyou! Ken C.