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Question 113228: 9(2x)=(9 x 2)x
Would this problem be commutative, assosiative, identity or a false statement.
Answer by Edwin McCravy(20077) (Show Source):
You can put this solution on YOUR website!
9(2x)=(9 x 2)x
You are using an x for both an unknown and also for
the multiplication sign. That makes it confusing.
So I'll use an askerisk * to denote multiplication.
9(2x) then means 9*(2*x)
(9 x 2)x then means (9*2)*x
So the equation you have is
9*(2*x) = (9*2)*x
You are comparing 9*(2*x) with (9*2)*x.
Suppose x represents 3. Then
9*(2*x) = (9*2)*x
means
9*(2*3) = (9*2)*3
The left side of 9*(2*3) = (9*2)*3 is done this way:
We start with 9*(2*3). Then we do what's in the
parentheses first and change the (2*3) to (6).
That makes 9*(2*3) become 9*(6)
Then 9*(6) means 9*6 which comes out 54
Now let's do the right side of 9*(2*3) = (9*2)*3:
Starting with (9*2)*3, we do what's in the parentheses
first and change the (9*2) to (18).
That makes (9*2)*3 become (18)*3
Then (18)*3 means 18*3 which also comes out to equal 54.
Therefore 9*(2*x) = (9*2)*x is a true whenever x = 3.
Let's pick another number for x to see if it is true
when x is that number. Suppose we pick 1 for x this
time.
Then
9*(2*x) = (9*2)*x
means
9*(2*1) = (9*2)*1
The left side of 9*(2*1) = (9*2)*1 is done this way:
We start with 9*(2*1). Then we do what's in the
parentheses first and change the (2*1) to (2).
That makes 9*(2*1) become 9*(2)
Then 9*(2) means 9*2 which comes out 18
Now let's do the right side of 9*(2*1) = (9*2)*1:
Starting with (9*2)*1, we do what's in the parentheses
first and change the (9*2) to (18).
That makes (9*2)*1 become (18)*1
Then (18)*1 means 18*1 which also comes out to equal 18.
Therefore 9*(2*x) = (9*2)*x is a true whenever x = 1.
Let's pick another number for x to see if it is true
when x is that number. Suppose we pick 87 for x this
time.
Then
9*(2*x) = (9*2)*x
means
9*(2*87) = (9*2)*87
The left side of 9*(2*87) = (9*2)*87 is done this way:
We start with 9*(2*87). Then we do what's in the
parentheses first and change the (2*87) to (174).
That makes 9*(2*87) become 9*(174)
Then 9*(174) means 9*174 which comes out 1566
Now let's do the right side of 9*(2*87) = (9*2)*87:
Starting with (9*2)*87, we do what's in the parentheses
first and change the (9*2) to (18).
That makes (9*2)*87 become (18)*87
Then (18)*87 means 18*87 which also comes out to equal 1566.
Therefore 9*(2*x) = (9*2)*x is a true whenever x = 87.
So 9*(2*x) = (9*2)*x
must be true no matter what number x is.
They both involve multiplying three quantities,
9, 2 and x.
In 9*(2*x) the parentheses are ASSOCIATING the
2 and the x together
In (9*2)*x the parentheses are ASSOCIATING the
9 and the 2 together.
So it's the ASSOCIATIVE PRINCIPLE that is being
demonstrated here.
Edwin
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