Try It Yourself#

Exercise 1#

Find the derivative of the function \(f(x) = 5x^2 - 2x\) using the limit definition of the derivative.

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Answer: \(10x - 2\)

Exercise 2#

Evaluate \(f'(x)\) for \(f(x)= 3x^2 + 5x^{-2} + 7\sqrt{x}\) using the basic rules of differentiation.

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Answer: \(6x - 10x^{-3} + \frac{7}{2}x^{-1/2}\)

Exercise 3#

Evaluate \(f'(x)\) for

\[f(x)= \dfrac{7}{x^7} + \dfrac{5}{x^5} + \dfrac{3}{x^3}.\]

(Avoid using the quotient rule by rewriting each term so that it involves multplying by a negative power of \(x\).)

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Answer: \(-49x^{-8} - 25x^{-6} - 9x^{-4}\)

Exercise 4#

Find the equation of the tangent line of

\[f(x)=\dfrac{x^{\frac{3}{2}}+x^{\frac{1}{2}}+1}{x^2} \text{ at } x=4.\]

(Avoid using the quotient rule by dividing each term of the numerator by \(x^2\) and then simplifying.)

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Answer: \(y = -\frac{9}{64}(x-4) + \frac{11}{16}\)

Exercise 5#

Evaluate \(f'(x)\) for

\[f(x)= (x^3+6)(x-2)(x+2).\]

(Simplify \((x-2)(x+2)\) and then apply the product rule.)

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Answer: \(5x^4 - 12x^2 + 12x\)

Exercise 6#

Evaluate \(f'(x)\) for

\[f(x)= \sqrt{\dfrac{x^2-1}{x+1}}.\]

(Simplify the function before computing the derivative.)

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Answer: \(\frac{1}{2\sqrt{x-1}}\)

Exercise 7#

Evaluate \(f'(x)\) for

\[f(x)=\dfrac{17}{(3x+4)^2}.\]

(Rewrite the function before differentiating in order to avoid using the quotient rule.)

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Answer: \(-\frac{102}{(3x+4)^3}\)

Exercise 8#

Evaluate \(f'(x)\) for \(f(x)=5x^4(x^3+6)^{7}\) and simplify your answer.

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Answer: \(5x^3(x^3+6)^6(25x^3 + 24)\)

Exercise 9#

Evaluate \(f'(x)\) for \(f(x)=\dfrac{(x^2+4)^5}{(x^6+ 1)^3}\) and simplify your answer.

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Answer: \(\frac{2x(x^2+4)^4(-4x^6-36x^4+5)}{(x^6+1)^4}\)

Exercise 10#

Evaluate

\[\displaystyle\lim_{h\to 0}\dfrac{(1+h)^5-1}{h}.\]
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Answer: \(5\)

Exercise 11#

Draw the graph of a function \(f(x)\) that is continuous at \(x=a\) but not differentiable at \(x=a\). Explain why the function is continuous but not differentiable at this point.

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Answer: Consider a graph with a corner or a vertical tangent line