Minimum of f(x) = x² + 4:

💡 x² ≥ 0; minimum when x = 0.

Find x that minimises f(x) = (x − 5)²

💡 Vertex of parabola.

Gradient descent on f(x) = x² with learning rate 0.1, start x = 5. Value after 1 step?

💡 x ← x − α·∇f. ∇f = 2x.