# Thread: how to find equation of polynomial from a graph

1. ## how to find equation of polynomial from a graph

how to find equation of polynomial from a graph

2. Originally Posted by supersaiyan
how to find equation of polynomial from a graph
That depends. Do you have the graph to show us?

A polynomial of degree n can always be expressed as
$\displaystyle f(x) = a(x - r_1)(x - r_2)...(x - r_n)$
where the r's are the x-intecepts of the graph. The problem is that roots are not always real, and thus do not show up on the graph.

It would be best if you showed us your problem so we could tell you what cases you need to consider, etc.

-Dan

3. You can also pick (n+1) points (assuming you know its degree at least) and create a system of equations and solve them. (Which is extremely messy in general but it always works).