title: R- Equation with additional condition. Vector condition
body: <p>I've got a problem with computing some expression like this:</p>
  
  <p><a href="https://imgur.com/l4YEZ5I" rel="nofollow">equation</a></p>
  
  <p>I tried use solve function but it shows me matrix must be n x n size.
  If someone encountered similar problem please help me or give some sources ;)</p>