How to use correctly fsolve

Hi everyone, i don't be able to find the way to write a nonlinear system. Can you help me? The system is substantially in this form:

1) (x(i+1)-x(i))*(y(i+1)-y(i))+x(i-1)-y(i-1);

2) (x(i+1)-2x(i))-y(i)

Answer 1

[Walter Roberson]

Vectorize

diff(x(3:end)) .* diff(y(2:end-1)) + x(1:end-1) - y(1:end-1)

x(3:end) - 2 * x(2:end-1) - y(2:end-1)