For those values of k, verify that every member of the family of functions
y = A sin(kt) + B cos(kt)
is also a solution.
y = A sin(kt) + B cos(kt) ⇒ y' = Ak cos(kt) − Bk sin(kt) ⇒ y'' = −Ak2 sin(kt) − Bk2 cos(kt).

the answer is 15% decrease

idk man good luck man

hello from mrbilldoesmath!

answer:

(7 x + 6 y) (49 x^2 - 42 x y + 36 y^2)

discussion:

the trick is to recognize that 343 = 7^3 and 216 = 6^3 and, in general,

a^3 + b^3 =   (a + b) (a^2 - a b + b^2).

in our case

343x^3+216y^3   =   (7x)^3 + (6y)^3

so take a = 7x and b = 6y in the above equation to get the answer.

you,

mrb