... a12β + a 13 γ,kβ = a21α + a22β + a 23 γ,kγ = a 31 α + a 32 β + a 33 γ,hay l`a(a11−k)α + a12β + a 13 γ =0,a21α +(a22− k)β + a 33 γ =0, (14.60)a 31 α + a 32 β +(a 33 − k)γ =0.Hˆe.(14.60) ... thuˆa`n nhˆa´t sau 13. y (3) + y(2)= 1. (DS. y = C1+ C2x + C 3 e−x+x22)14. 3y(4)+ y (3) = 2. (DS. y = C1+ C2x + C 3 x2+ C4e−x 3 +x 3 3)15. y(4)− 2y (3) +2y(2)−2y+ ... C 3 x 3 ,y(t)=C1y1+ C2y2+ C 3 y 3 ,z(t)=C1z1+ C2z2+ C 3 z 3 ,hay l`ax(t)=C1α1ek1t+ C2α2ek2t+ C 3 α 3 ek 3 t,y(t)=C1β1ek1t+ C2β2ek2t+ C 3 β 3 ek 3 t,...