能完成的追加50分

[x,y]=dsolve('D2x+2*Dx=x+2*y-exp(-t)','Dy=4*x+3*y+4*exp(-t)','t')
x =
25/(2*exp(t)) - (C5*exp(t + 6^(1/2)*t))/5 - (C6*exp(t - 6^(1/2)*t))/5 - C4/exp(t) + (6^(1/2)*C5*exp(t + 6^(1/2)*t))/5 - (6^(1/2)*C6*exp(t - 6^(1/2)*t))/5 - (66*t)/(exp(t)*(4*6^(1/2) + 11)) - (24*6^(1/2)*t)/(exp(t)*(4*6^(1/2) + 11))
y =
(8*C5*exp(t + 6^(1/2)*t))/5 - 12/exp(t) + (8*C6*exp(t - 6^(1/2)*t))/5 + C4/exp(t) + (2*6^(1/2)*C5*exp(t + 6^(1/2)*t))/5 - (2*6^(1/2)*C6*exp(t - 6^(1/2)*t))/5 + (66*t)/(exp(t)*(4*6^(1/2) + 11)) + (24*6^(1/2)*t)/(exp(t)*(4*6^(1/2) + 11))