Mathematical tools for intermediate economics classes
Iftekher Hossain

Derivatives and their uses

Section 5

Practise questions

Question 4 Find the first-order and the second-order derivatives

a) \(f(x) = 10x + 2\)
b) \(f(x) = 80x - 2x^{2}\)
c) \(f(x) = 35 + 5x - 4x^{2} + x^{3}\)
d) \(f(x) = 90x^{2} - x^{3}\)
e) \(f(x) = (2x - 4)^{4}\)
f) \(f(x) = 2 \sqrt{x}\)
g) \(f(x) = 2q^{3} - 12q^{2} + 30q\)
h) \(f(x) = q^{3} - 9q^{2} + 45q\)

a) \({f}'(x) = 10\)              \({f}''(x) = 0\)
b) \({f}'(x) = 80 - 4x\)            \({f}''(x) = -4\)
c) \({f}'(x) = 5 - 8x + 3x^{2}\)          \({f}''(x) = -8 + 6x\)
d) \({f}'(x) = 180x - 3x^{2}\)          \({f}''(x) = 180 - 6x\)
e) \({f}'(x) = 8(2x - 4)^{3}\)           \({f}''(x) = 48(2x - 4)^{2}\)
f) \({f}'(x) = \frac{1}{x^{0.5}}\)              \({f}''(x) = -0.5x^{-1.5}\)
g) \({f}'(x) = 6q^{2} - 24q + 30\)        \({f}''(x) = 12q - 24\)
h) \({f}'(x) = 3q^{2} - 18q + 45\)        \({f}''(x) = 6q - 18\)



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