Algebra

Misreading Function Notation as Multiplication

Students read f(3)f(3) as f×3f \times 3 instead of the output of function ff when the input is 33.

Quick check

Why students make it

In algebra, letters next to parentheses often mean multiplication, like 3(x+2)3(x+2). The notation f(x)f(x) looks similar, so students treat the function name ff like a variable factor.

The rule done right

In function notation, f(a)f(a) means substitute aa for every xx in the rule for ff. It does not mean f×af \times a unless ff is being used as a number, not a function.

Related resources

function-notationsubstitutionalgebra