[4_linear_algebra]_add_:math:

[shlff]

Hi @jstac , this PR adds ":math:" to L and u in the following sentence of lecture linear_algebra:

• which is the first-order condition for maximizing L w.r.t. u.

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🚀 Deployed on https://5fe91b1582357503036a3ffb--practical-lalande-b89631.netlify.app

[jstac]

Good catch, thanks @shlff