format long
x0=0.3-0.5488;
x1=0.4-0.4493;
x2=0.5-0.3679;
x3=0.6-0.3012;
y0=0.3; y1=0.4; y2=0.5; y3=0.6;
x=(0-x1)*(0-x2)*(0-x3)*y0/(x0-x1)/(x0-x2)/(x0-x3)+(0-x0)*(0-x2)*(0-x3)*y1/(x1-x0)/(x1-x2)/(x1-x3)+(0-x0)*(0-x1)*(0-x3)*y2/(x2-x0)/(x2-x1)/(x2-x3)+(0-x0)*(0-x1)*(0-x2)*y3/(x3-x0)/(x3-x1)/(x3-x2);
y=x-exp(-2*x);
x
y