Как решить систему уравнений в паскаль?

 const 
  x: array[0 .. 3] of real = (0.4, 2, 4.1, 5.8); 
 
var 
  i: integer; 
  y: real; 
 
begin 
  for i := 0 to Length(x) - 1 do 
  begin 
    if x[i] < 1 then 
      y := x[i] * x[i] + 4 
    else if (x[i] >= 1) and (x[i] <= 3) then 
      y := Ln(x[i] + 3) 
    else if (x[i] > 3) and (x[i] <= 5) then 
      y := 2 * trunc(x[i]) + 1 
    else 
      y := trunc(x[i]); 
    writeln('y(', x[i]:0:1, ') = ', y:0:4) 
  end; 
end.