R optimization with equality and inequality constraints

Question

I am trying to find the local minimum of a function, and the parameters have a fixed sum. For example,

Fx = 10 - 5x1 + 2x2 - x3

and the cond

Answer 1

rewrite

fx = function(x) {10 - (5*x[1] + 2*x[2] + (15 - x[3] - x[2]))}

and add the additional constrain that

x[1] + x[2] <= 15