
:pre-calculus, precalculus, function, variable,
evaluate, substitution, replace, composed function, compose

:operation, substitute
variable, x

:, Substitute

:<TD VALIGN=TOP ALIGN=center>
 In function f(x) =
 <INPUT NAME="formula" TYPE="text" SIZE=45 VALUE="x^2 + 3*x + 1">
 <TR><TD NOWRAP style="text-align:center;">
 $submit1 x by
 <INPUT NAME="formula2" TYPE="text" SIZE=20 VALUE="1 + t">

