a=1/13
x1/a=3s-2c
x1'/a=3(3c+2s)
x1''/a=9(-3s+2c)
(x''+2x'+5x)/a=(-27+2*6+5*3)s+(18+2*9-5*2)c=26c
x''+2x'+5x=26ac=2c