2∂∂∂∂YYXX∂ - 2∂ + 9∂ + 2∂ + 9U = 0 ∂ - 922UU2UUU

1. - BAI TAP CHO 16 UNIT 12 CO DAP AN
BAI TAP CHO 16 UNIT 12 CO DAP AN
1.

2

∂yx∂ - 2∂ + 9∂ +

2

∂ + 9u = 0 ∂ - 9

2

u

2

u