Substituting Other Variables

You don’t always have to substitute numbers into a function; sometimes you can substitute another variable.

For instance if f(x) = 3x+2, you could substitute the generic x with a more specific variable, here designated a. Thus, if the variable a is substituted for x, we would be finding f(a):

Just as f(1) meant to substitute the number 1 for all x's, so f(a): means substitute a for all x.

f(x) = 3x + 2
f(a) = 3a + 2
f(1) = 3•1 + 2

Play the substitution blackboard cartoon (Flash) again to see how it works.