Suppose That Y₁ and Y₂ Are Both Solutions of the Differential

Suppose that Y₁ and Y₂ are both solutions of the differential equation .
Which of the following must also be solutions of this differential equation? Select all that apply. Here, C₁ , and C₂ are arbitrary real constants.

A) $5 y_{1}-4 y_{2}$
B) $t y_{1}$
C) $C_{1}$
D) $\left(C_{1} y_{1}\right) \cdot\left(C_{2} y_{2}\right)$
E) $C_{1}\left(y_{1}+y_{2}\right)$
F) $C_{1}\left(7 y_{1}-9 y_{2}\right) -C_{2}\left(2 y_{1}-7 y_{2}\right.$