By Taylor's theorem for real functions of two variables,
So
Nm160111 (talk) 02:29, 26 November 2012 (UTC)Reply
Too complex for examples, but saves work when making them.
By Taylor's theorem,
So
Which we can rearrange as
Given this, we now attempt to choose coefficients and such that
This can be done by solving the following system of equations in unknowns:
By setting all to be constant, the system of equations may be made linear.
Nm160111 (talk) 02:29, 26 November 2012 (UTC)Reply