matlab四维参数拟合问题

Question

四维方程y=ax1+x2(πbx3^2-2/3πcx3^3),a,b,c为未知参数待拟合，x1,x2,x3为变量，求拟合方程怎么编程。QQ：724429983。。诚心谢谢好人
x1=1.3311, 3.8836, 6.1042, 7.9581, 12.1415, 17.6534, 22.1343, 26.0562, 27.9412;
x2=15.46, 42.1, 66.05, 79.01, 119.99, 149.22, 320.23, 390.85, 416.5;
x3=0.12, 0.05, 0.038, 0.03, 0.026, 0.014, 0.01, 0.007, 0.004;
y=9.45, 11.1, 13.3, 14.7, 19.85, 27, 31, 37, 38.3

Answer 1

用matlab的nlinfit（）函数，求得

执行代码：