Problem 1
Use the precise definitions, state all hypotheses, apply f'(a)=lim_{h→0}(f(a+h)-f(a))/h, and verify the conclusion against a boundary case or independent theorem.
Faculty solution guide
Derivative as a Limit and Linear Approximation
Accept equivalent mathematically correct reasoning. Require explicit definitions, theorem hypotheses, proof structure, verification, and limitations.
Problem 2
Identify the first invalid inference, missing hypothesis, quantifier error, unjustified limit interchange, or unproved existence claim; then supply a valid repair.
Problem 3
A complete response explicitly states the definitions, domain, hypotheses, exact target, and theorem dependencies for Derivative as a Limit and Linear Approximation.
Problem 4
The argument must address proving differentiability from difference quotients with each nontrivial step justified and the final conclusion restated.
Problem 5
A strong application explains the mathematical model in optimization, sensitivity, approximation, dynamical systems, and numerical analysis, verifies conditions, and names at least one limitation.
Problem 6
Accept a second valid proof, a counterexample showing necessity of a hypothesis, an independent estimate, or a reproducible finite check that is correctly described as supporting evidence.