minf=(5.3*x1+8.5*x2+8.8*x3)/(x1+x2+x3)x1+x2+x3=140x1>=15x2>=30x3>=30求x1,x2,x3的最优解,用matlab怎么编程啊,弄了好多天都不懂,跪求高手帮忙