Khan Academy

The Lagrangian (K-A)

Examples: Second partial derivative test (K-A)

Maxima, minima, and saddle points (K-A)

Reasoning behind second partial derivative test (K-A)

Second partial derivative test (K-A)

Multivariable maxima and minima (K-A)

Saddle points (K-A)

Second partial derivative test example, part 1 (K-A)

Second partial derivative test example, part 2 (K-A)

Second partial derivative test intuition (K-A)

Second partial derivative test-video (K-A)

Warm up to the second partial derivative test (K-A)

Expressing a quadratic form with a matrix (K-A)

Quadratic approximation example (K-A)

Quadratic approximation formula, part 1 (K-A)

Quadratic approximation formula, part 2 (K-A)

The Hessian (K-A)

The Hessian matrix (K-A)

Vector form of multivariable quadratic approximation (K-A)

Computing a tangent plane (K-A)

Vector form of multivariable quadratic approximation-video (K-A)

Controlling a plane in space (K-A)

What do quadratic approximations look like (K-A)

Local linearization (K-A)

Local linearization-video (K-A)