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## Main Question or Discussion Point

Let s be a column vector and L be a diagonal matrix. Then

[tex]s^T L s L s = L s s^T L s [/tex]

by noticing that [tex] s^TLs[/tex] is a scalar.

However,

[tex] s^T L s L \neq L s s^T L [/tex].

Is there some mathematical explanation behind this? Thank you.

elgen

[tex]s^T L s L s = L s s^T L s [/tex]

by noticing that [tex] s^TLs[/tex] is a scalar.

However,

[tex] s^T L s L \neq L s s^T L [/tex].

Is there some mathematical explanation behind this? Thank you.

elgen