1)The function g is twice differentiable at R and true:g(-1)=7.to show that the function

f(x)=3(x-2)ēg(2x-5)

is twice differentiable at R and find the slope of f' at xo=2

2)for the function f are:

i)is twice differentiable at R

ii)is unnecessary

iii)the slope of the point xo=-1 is -2

to show that the function

g(x)=f(x)cosx-f(cos)

is twice differentiable at R to find the number g''(0)

can slove this exercises to help me?

p.s iam new at the forum iam from greece and sorry for my english the exercises were translated verbatim from GR to EN with google translation

Thanks in advance