Question

How do I find `f(3)` from the graph of `f(x) = x^2 - 4x + 3`?

Answer 1

From the graph, by just looking and guessing.

Explanation:

This is the graph of that function:
graph{x^2-4x+3 [-2, 6 -3, 8]}
At `x=3`, you can clearly see that the graph crosses the x-axis, where there's a `y`-value of `0`. `f(3)` is thus equal to `0`.