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

:operation, substitute
variable, x

:, Substitute

:
 In function f(x) =
 <input name="formula" type="text" size="45" value="x^2 + 3*x + 1">
 $submit1 x by
 <input name="formula2" type="text" size="20" value="1 + x">
