TI-84 Plus CE field manual for IB Math
Building a table of values
Store a function, choose the x-values the table runs over, and read the value column; then switch the table to Ask so it evaluates x-values you type.
Tabulate f(x)=x3−4x+1 for x=−3 to x=3 in steps of 1, then evaluate f(2.5).
Store the function. Press and type it into Y1 with . Use for the subtraction, not the negative key beside ENTER.
Set up the table. Press for TBLSET. Set TblStart to the first x-value you want with , and ΔTbl to the step with . Leave Indpnt and Depend on Auto.
Press for TABLE. The X column counts up from −3 in steps of 1 and Y1 holds the matching values. Scroll with and to extend the table in either direction; new rows are generated as you scroll.
Read what the column tells you. Y1 changes sign three times: between x=−3 and x=−2, between x=0 and x=1, and between x=1 and x=2. A sign change means a root in between, so this cubic has all three of its roots inside the table.
Now evaluate the function at a value of your choosing. Go back with , move down to Indpnt and set it to Ask with . Press again: the table is empty, and whatever you type into the X column is evaluated on . Type .
f(2.5)=6.63 to 3 s.f., and the Auto table brackets all three roots.
Your turn
Work each one on your calculator, then check the answer.
- 1
Tabulate f(x)=x3−6x+2 from x=−3 to x=3 in steps of 1. Between which pairs of consecutive integers does f change sign? Then find f(1.4).
- 2
Tabulate f(x)=ex−4x from x=−3 to x=3 in steps of 1. Between which pairs of consecutive integers does f change sign? Then find f(1.7).
- 3
Tabulate f(x)=x4−5x2+2 from x=−3 to x=3 in steps of 1. Between which pairs of consecutive integers does f change sign? Then find f(2.2).