Differentiate Part 2 Homework: F(y)=5+14/y\hat{}2+9/y\check{}4

[jimen113]

Homework Statement

RE: F(y)= (1/y\hat{}2 - 3/y\hat{}4)(y+5y)
the answer is: F=5+14/y\hat{}2+9/y\check{}4

The Attempt at a Solution

F(y)= (f*g)\acute{}
f\acute{}*g)+(f*g\acute{})

(-2y\hat{}-3+12y\hat{}-5)*(y+5y\hat{}3)+(y\hat{}-3-3y\hat{}-4)*(1+15y\hat{}2)
so, I get (14/y\hat{}2 +9/y\hat{}4)+5y,
which is very close to the answer in the book, except that instead of 5y they have the answer as just (14/y\hat{}2 +9/y\hat{}4)+5
??

 

[sutupidmath]

I cannot clearly read what you did, but you first need to apply the product rule tha is
let f(y)=y^{-2}-3y^{-4}, \ \ and \ \ \ g(y)=6y so

F(y)=f(y)*g(y)=>F'(y)=f'(y)*g(y)+g'(y)*f(y)

or you could merely foil everyghing out and you would end up with:

F(y)=6y^{-1}-18y^{-3} and then take the derivative of this one.


However i think that you originally gave us the wrong function, for there is no way you can get the answer you provided us. check it again, for i won't do it for you. Because by just integrating the result you gave us, one cannot get the function you provided.