(用matlab画相平面图)x'=2x+3y,y'=2x+y,x(0)=-2.7,y(0)=2.8 0<t<10...答:(2) x’=2x+3y, y’=2x+y, x(0)=-2.7,y(0)=2.8, 0<t<10, 作相平面图。解:使用matlab工具:先解微分方程组:x’=2x+3y, y’=2x+y, x(0)=-2.7,y(0)=2.8, 0<t<10,(1)建立.m文件:funtt.m function y=funtt(t,y)[2*y(1)+3*y(2);2*y(1)+y(2)];...