Please help! MEDAL + FAN! (fairly easy question)

For the graph below, what should the domain be so that the function is at least 200?

Question

Please help! MEDAL + FAN! (fairly easy question) 

For the graph below, what should the domain be so that the function is at least 200?

anonymous · Answer

attachment

anonymous · Answer

a. −5 ≤ x ≤ 20
b. 0 ≤ x ≤ 15
c. x ≥ 0
d. All real numbers

I'm really not sure what the answer is. I think it's A but another post said B, so I'm just confused. I suck at determining domains.

anonymous · Answer

Is it B?

triciaal · Answer

the domain is the set of x values that satisfies the function

triciaal · Answer

you want y to be 200 or more 
find the line y = 200 then read the set of x

triciaal · Answer

yes B

anonymous · Answer

Oh, so it's 15 because it hits the same line as 200 on the parabola?

triciaal · Answer

domain set of values    0 to 15  yes 15 included because it y at least 200  when x = 15 y = 200   at least means the lowest value allowed and includes what is more than that value

anonymous · Answer

Oh okay! Thank you so much! :D