解:微分方程为2dx/dt=5dy/dt+4y-x,3dx/dt=4dy/dt+2x-y;化为2x'+x-(5y'+4y)=0,3x'-2x-(4y'-y)=0,设微分方程的特征值为p,特征方程为(2p+1)(-4p+1)-(3p-2)(-5p-4)=0,(2p+1)(4p-1)-(3p-2)(5p+4)=0,8p²+2p-1-(15p²+2p-8)=0,得:p=±1,微分方程的特征根为eᵗ、e⁻ᵗ;设x=aeᵗ+be⁻ᵗ,y=ceᵗ+de⁻ᵗ,有2(aeᵗ+be⁻ᵗ)'+aeᵗ+be⁻ᵗ=5(ceᵗ+de⁻ᵗ)'+4(ceᵗ+de⁻ᵗ),得:a=3c,b=d,微分方程的通解为x=3ceᵗ+be⁻ᵗ,y=ceᵗ+be⁻ᵗ(b、c为任意常数)
解常微分方程
微分方程化为2x'=5y'+4y-x,3x'=4y'+2x-y;化为
3(5y'+4y-x)=2(4y'+2x-y),15y'+12y-3x=8y'+4x-2y,x=y'+2y,有2(y'+2y)'=5y'+4y-(y'+2y),2y"+4y'=4y'+2y,y"=y,微分方程组的特解为y=aeᵗ+be⁻ᵗ(a、b为任意常数),x=3aeᵗ+be⁻ᵗ