Question

Why is the determinant of x'x(x transpose x) 0 ?

Answer 1

multiplied by zero?

Answer 2

No no the determinant of x'x is 0 ...my question is how ?

Answer 3

\[
x=\left(
\begin{array}{cc}
1 & 2 \\
3 & 5 \\
\end{array}
\right)
\]

Answer 4

\[
x'=\left(
\begin{array}{cc}
1 & 3 \\
2 & 5 \\
\end{array}
\right)
\]

Answer 5

\[
x x'=\left(
\begin{array}{cc}
5 & 13 \\
13 & 34 \\
\end{array}
\right)\]

Answer 6

So Det(x x')=1, so it is not zero in general

Answer 7

Also Det[ x'x]=1