HELP! During the period 1998–2002, the number y (in millions) of juvenile books shipped to bookstores can be modeled by the equation y = -15x^2 + 64x + 360 where x is the number of years since 1998.

During what year were there 400 million juvenile books shipped to bookstores?

Question

HELP! During the period 1998–2002, the number y (in millions) of juvenile books shipped to bookstores can be modeled by the equation y = -15x^2 + 64x + 360 where x is the number of years since 1998.

During what year were there 400 million juvenile books shipped to bookstores?

anonymous · Answer

y = -15x^2 + 64x + 360 
400 = -15x^2 + 64x + 360
-15x^2 + 64x - 40 = 0
sol ve this for x

anonymous · Answer

- a bit messy this one!

anonymous · Answer

i think this is best solved using  the quadratic formula

anonymous · Answer

Year of 2001?

anonymous · Answer

400=-15x^2 + 64x + 360

anonymous · Answer

if year is 2001, ...
y=-15(2001)^2 + 64(2001) + 360

anonymous · Answer

x = year, ok?

anonymous · Answer

hold on - solving 
x = 4.82
so that must be 1998 + 5 = 2003

anonymous · Answer

ooopps - i made an error solvig

anonymous · Answer

i got my signs wrong
correct is x = 3.51 or 0.76

anonymous · Answer

Which would be 1998 + 3.51?
= 2001.51
or 2001?

anonymous · Answer

- yes thats a good question
- i think it must be 2001 because 2001 . 51 is half way through that year

anonymous · Answer

Thank you! :)

anonymous · Answer

yw - good luck