Why I get a syntax error on desolve

[Anthony The Koala]

I am exploring derivatives in the HP Prime.

I solved a 2nd order ode
desolve(4*y''-6*y'+7*y=0)

I successfully get
G_0*cos(1/4*19^0.5*x) + G_1*sin(1/4*19^0.5*x))*exp(3/4*x)

BUT at a later time I solve the same equation.

It now adds the "CAS." before desolve

CAS.desolve(4*y''-6*y'+7*y=0)

I now get
X Error:Syntax Error

Why?

Thank you
Anthony, Sydney