Pure 1 help.

[mousa]

Hello, i need help with those couple of questions
Thanks in advance.

Sera’s grandparents put $1000 into a savings bank account
for her every year since her age of 10. The account pays
interest at 6% per year. (a) How much money is in the
account at her age of 18. (b) Find the estimate age in year,
that the amount in the account exceeding $20,000

Given that the expansion of (1 + ax)^n begins 1 +
36x + 576x^2, find the values of a and n.
Simplify (1 – x)^8 + (1 + x)^8. Substitute a suitable
value of x to find the exact value of 0.99^8 + 1.01^8

[mousa]

Another one 

For each of the following functions f(x), find f’(x) and
any intervals in which f(x) is (i) decreasing and
(ii) increasing.
(b) x^4 – 4x^3

[nid404]

Another one 

For each of the following functions f(x), find f’(x) and
any intervals in which f(x) is (i) decreasing and
(ii) increasing.
(b) x^4 – 4x^3

where r the functions?

[astarmathsandphysics]

differentiate
4x^3 -12x^2 =4x^2(x-3)>0 hence increasing if x>3 and 4x^2(x-3)<0 if x<3 , x not equal 0 hence decreasing,

[astarmathsandphysics]

The first questions answered here