Answer:

Step-by-step explanation:
The half life is the amount of time it takes a substance to decay to half of its original amount.
Since the radioactive substance has a half life of 1000 years, there will be half of it left after 1000 years.
So, the fraction that will be left after 1000 years is 
Step-by-step explanation:
Hi,
For the first screenshot, your answer will be...
A) 1/10 + 1/4 ≤ 1
And for the second screenshot, your answer will be...
A) d ≤ -1/2n + 5
I hope this helps :)
Answer:
D) c - 2 = 25 + c + 10√c
Step-by-step explanation:
The given equation is 

Taking square on both sides, we get
Here we used ( a+ b)^2 = a^2 + b^2 + 2ab formula.
c - 2 = 5^2 + (√c)^2 + 2(5)√c
c - 2 = 25 + c +10√c
Answer: D) c - 2 = 25 + c + 10√c
Thank you.

Then using trygonometric table or a graph we read that:

Period of cosinus function = 2π
So the last answer is