to access the second derivative option
which algebraically finds the second derivative of an expression
with respect to a variable at a value. If the value is omitted,
the current value of the variable is used.
Next, enter an expression, the variable, and a value
separated by commas. For example, to find the second derivative of y = x4
at x = 2, enter
For f(x) = x3, f"(2) = 48.
Note: Unfortunately, the TI cannot differentiate some functions
algebraically. For these functions use the less accurate
numerical differentiation option nDer twice.