Question

The solution of (D? - D'?)z = cos(x + y) is​

Answer 1

The auxiliary equation for the given equation is m2 ∴ + m – 2 = 0, which gives m = 2, 1 C.F. of the given partial differential equation is z=ϕ1( y−2x)+ϕ2( y+x) where ϕ1 and ϕ2 are arbitrary functions.