Answer:
f(x) = x
Step-by-step explanation:
f(x) = x is of the form y = mx + b.
y = mx + b is the slope-intercept form of the equation of a line, so its graph is a line.
f(x) = x^2 has a variable to the second power, so its graph is a parabola, and not a line.
f(x) = |x| has an absolute value, so its graph is shaped like a V. It is not a line.
