미분방정식 $y ''+6y '+25y= \delta \left (t-2 \right), y (0) =y ' (0) =0$ 을 만족하는 함수 $y (t)$ 는?

• ①$\displaystyle \frac{1} {4} e ^ {-3 \left (t-2 \right)} \cos \left (4 \left (t-2 \right)) u (t-2 \right)$
• ②$e ^ {-3t} \cos \left (4 \left (t-2 \right) \right) u \left (t-2 \right)$
• ③$\displaystyle \frac{1} {4} e ^ {-3 \left (t-2 \right)} \sin \left (4 \left (t-2 \right) \right) u \left (t-2 \right)$
• ④$e ^ {-3t} \sin \left (4 \left (t-2 \right) \right) u \left (t-2 \right)$