Let $f(x) = 5x^4 - 3x^2$.

1. ​Write the equation of the line tangent to $y = f(x) \operatorname{at} x = 1$.

   Hint (a):

   Use the slope, which is $f′(1)$, and the point $(1, f(1))$ to write the equation.

2. Use your tangent line to approximate $f(1.1)$.

   Answer (b):

   $≈ 3.4$

3. Is the approximation an overestimate or an underestimate of the actual value?

   Hint (c):

   If $y = f(x)$ is concave up at $x = 1$, then the approximation is an underestimate.