There are a couple of ways
to solve this problem. Probably the easiest way
would be to go through your list of given equations
and begin substituting the values of X and Y as
given in the table. Once you find the equation
that has all three pairs of X and Y that work,
you have found the correct answer.
As soon as you find one set of X and Y that
won't work for the equation, you can move on
to the next equation.
Let's begin with the letter D, since we seem
to start with letter A all the time. Let's substitute
1 for X and 1 for Y and see if the equation works.
Y = X - 2
1 = 1
- 2
1 = -1
This statement isn't true, so we can move on to
the next equation, letter C.
X = Y + 2
1 = 1
+ 2
1 = 3
This statement isn't true either since 1 doesn't
equal 3. Move on to the next equation, letter
B.
Y = 2X - 1
1 = 2(1)
- 1
1 = 2 - 1
1 = 1
The first numbered pair works, so let's try the
next one.
Y = 2X - 1
3 = 2(5)
- 1
3 = 10 - 1
3 = 9
Since the second numbered pair doesn't work,
we know that this equation doesn't work for all
points. So it is on to the last one, letter
A.
X = 2Y - 1
1 = 2(1)
- 1
1 = 2 - 1
1 = 1
So far so good. Let's try another set of numbers.
X = 2Y - 1
5 = 2(3)
- 1
5 = 6 - 1
5 = 5
Another one works! This one is looking good. One more to try
to make sure.
X = 2Y - 1
7 = 2(4)
- 1
7 = 8 - 1
7 = 7
Since all three pairs of X and Y worked with
the equation, you know that your answer to this
problem is letter A, X = 2Y - 1. Of course it
would be letter A when we decide to start from
the bottom and work our way up this time.
Final answer is letter A.
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