SAT math question

Test Preparation
1

<p>If this helps I am doing this practice problem from the 2007-08 SAT official practice test. Anyway I can't figure out this problem and I am hoping someone can explain it to me. </p>

<p>Chart: x y
<strong>|</strong>
(0, 100)
(1,99)
(2, 96)</p>

<p>Question: Which of the following equations describes y in terms of x for all ordered pairs in the table above?</p>

<p>(A) y=100-x²
(B) y=100-x
(C) y=100-2x
(D) y=100-4x
(E) y=100-100x</p>

<p>Any help would be greatly appreciated! Also if the chart doesn't makes sense just let me know :)</p>

2

<p>The chart gives 3 coordinates that lie on a graph of unknown form. A quick look at the chart tells us that the graph is not linear, because the slopes are different if you use different points Ex: (100-99)/(0-1)=-1 and (99-96)/(1-2) = -3. So the graph is not linear. All the choices are linear graphs except A, so A must be the correct answer.</p>

3

<p>The other way you can do it is to plug in the numbers into each equation and see what works.
(0,100) so x=0, y=100. Plugging them into the equations…Bummer - A, B, C, D, E are all true</p>

<p>(1,99)
Only A and B are true
99=100-1^2
99=100-1</p>

<p>(2, 96)
We only have to look at A and B and only A is true so that must be the answer.
96=100-2^2
(96 doesn’t equal 100-2)</p>

4

<p>Thanks for all the help :)</p>