Talk:Steffensen's method

Typo?

The "units" seem to be inconsistent in this formula at the end of the derivation:

$P=P_{n}-{\frac {(P_{n+2}P_{n}-P_{n+1})^{2}}{P_{n+2}-2P_{n+1}+P_{n}}}$

The numerator is subtracting $P_{n+1}$ from $P_{n+2}P_{n}.$ Suppose the values of P are distances measured in meters. Then $P_{n+1}$ has units of distance (meters) and $P_{n+2}P_{n}$ has units of area (meters^2). One cannot subtract a distance from an area. Is there a typo in the given formula? - Ac44ck (talk) 04:37, 26 December 2008 (UTC)