Casio fx-CG50 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).
Press and choose Table. The function list looks like the Graph mode one but is headed Table Func, and anything defined here is tabulated rather than plotted.
Type the rule into Y1 with , then . Use for the subtraction, not the negative key on the bottom row.
Set the range of x-values with (SET). Enter Start as , End as , and Step as , then . Unlike the other two calculators the Casio asks for an end as well as a start, so the table is finite and you choose its length here.
Press (TABLE) to generate it. The X column runs from −3 to 3 and Y1 holds the matching values, with the selected cell shown large at the bottom of the screen.
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 all three roots of this cubic sit inside the table.
To evaluate at a value of your own, edit the table in place. Move the cursor onto the X cell you want to replace, type and press . That row recomputes against the new x-value and the rest of the table is left alone.
f(2.5)=6.63 to 3 s.f., and the 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).