If y=Asin5x, then d2ydx2=
Differentiate y=Asin5x with respect to x,
dydx=5Acos5x
Again differentiate above equation with respect to x,
d2ydx2=−25Asin5x
=−25y
If 9x2+25y2=181 and xy=−6, find the value of 3x+5y.