nows the derivative is $y=3x^2$, and when $x=2$ the curve
    passes through $8$. So he writes an equation of the tangent
    line as $y-8=3x^2(x-2)$. What's wrong? What part of the general
    formula $y-f(c) = f'(c) (x-c)$ did Joe forget? <div class="review-answer">
    Joe forgot to replace $x$ with $2$ in the derivative.
    The equation should be $y-8=12(x-2)$. The notation $f'(c)$ is
    the part he forgot. He used $f'(x)=3x^2$ instead of $f'(2)=8$.</div>
  </div>

  <div class="problem" label="Tangen