In: Advanced Math
Suppose A is an mxn matrix of real numbers and x in an nx1 column vector.
a.) suppose Ax=0. Show that ATAx=0.
b.)Suppose ATAx=0. show Ax=0.
c.) by part a and b, we can conclude that Nul(A) = Nul(ATA), and thus dim(Nul A) = dim(Nul(ATA)), and thus nullity(A) = nullity(ATA). prove the columns of A are linearly independent iff ATA is invertible.