Which of the following functions opens downward?
y = –2x2 + x + 3
B
f(x) = 0.5x2 – X – 1

Problem number 26 of the rhind papyrus says: find a quantity such that when it is added to of itself the result is a 15. the modern day equation that models this problem is x + x = 15. what is the solution to the equation? x = 10 x = 12 x = 15 x = 30