Problem solving with quadratic functions.

[davie08]

Homework Statement

okay I know understand that I should get a reasonable understanding about the questions I post before I post them sorry about before.

An Illinois farmer will plant from 800 to 2000 acres of soybeans. The number of acres q that he will plant depends on the selling price per bushel p that is being paid in April. Suppose that if p=$10, then all 2000 acres will be planted, but if p=$6.25, then only 800 acres will be planted.

a)Assuming p and q are linearly related, find q as a function of p, giving a suitable domain.

Homework Equations

The Attempt at a Solution

for some reason this question seems to work out to be the opposite of what I've been doing with my other word problems, here's what I tried.

(2000,10) and (800,6.25)


m=6.25-10/800-2000 = .003125

q-q1 = m(p-p1)

q-2000 = .003125(p-10)

q-2000 = .003125p - .03125

q= .003125p + 1999.96875 800<q<2000


so this is the wrong answer and to get the right answer I have to make p my x and q my y. Then for the domain you find what it is for price.

But I just saw a tutor and she has it on a formula sheet that x=q and p=y.

 

[ArcanaNoir]

The number of acres q that he will plant depends on the selling price per bushel p

the clue here is "depends". Since q depends on p, p is the independent variable, which is always x.

 

[davie08]

okay thanks that makes sense.