Question

线代证明题

两个n维向量组A,B，A,B线性无关，证明:R(A,B)=R(A)+R(B)

Answer 1

知识点: 1.(AB)^T=B^TA^T 2.(A^T)^-1=(A^-1)^T 3.A是正交矩阵, 则A^T=A^-1 4.若AB=BA且A可逆, 则 A^-1B=BA^-1 证明: B^T=[(A+I)(A-I)^-1]^T = (A-I)^-1^T(A+I)^T ----知识点1 = (A-I)^T^-1(A+I)^T --知识点2 = (A^T-I^T)^-1(A^T+I^T) = (A^-1-I)^-1(A^-1+I) --知识点3 = (A^-1-I)^-1(A^-1A)(A^-1+I) = (I-A)^-1(I+A) = -(A-I)^-1(A+I) = -(A+I)(A-I)^-1 --知识点4 = -B. 所以B是反对称矩阵.