Math 251 Calculus III Quiz
2. (4 pts) Given f (x, y) = ln (x + 2y),
Find the directional derivative Duf at the point (1, 1) in the direction .
3. (7 pts) Given
(a). Find the linearization L (x, y) at the point (4, 0).
(b)Use the linearization L (x, y) from part (a) to
approximate the value of f(4.3,-0.2).
[ Simplify as much as possible (converting decimals to fractions at some point will help).
Remember one of the reasons for using linearizations is to have a decent way to approximate values without a calculator .]