Direct Proportion and The Straight Line Graph
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Straight line graphs that go through the origin, like the one immediately below, show that the quantities on the graph are in direct proportion. This graph states, therefore, that A is directly proportional to B. It also states that B is directly proportional to A, but we are going to work with the statement 'A is directly proportional to B'.
For the above graph:
This is how you write a direct proportion. The symbol in the middle is the Greek letter alpha.
It reads: A is directly proportional to B.
It means: By whatever factor A changes, B changes by the same factor.
So, let's look at the graph and see if by whatever factor A changes, B changes by the same factor.
This is what we are looking for, as we go from 'sub 1' to 'sub 2':
About the factor changes:
Below is an example of a point on this graph. The point is (B1, A1) and it has coordinates (1, 1).
For the above graph:
Coordinate for B1.
Coordinate for A1.
We will check for this shape of a graph if we change A by some factor, does B truly change by the same factor, thus showing that this straight line through the origin represents a direct proportion. In the graph below we change the quantity A by a factor of 3; that is, we triple it.
For the above graph:
Coordinates for (B1, A1).
Coordinates for (B2, A2).
Going from 'sub 1' to 'sub 2', A changes by a factor of 3. That is, A1 times a factor of 3 equals A2.
Going from 'sub 1' to 'sub 2', B also changes by a factor of 3. Likewise, B1 times a factor of 3 equals B2.
Both A and B change by the same factor. That factor is 3.
Therefore, A is directly proportional to B.
Again, the picture:
Let's try this below again for another point using the same graph. Here's the picture:
These steps show the factor changes:
For the above graph:
Coordinates for (B1, A1).
Coordinates for (B2, A2).
Going from 'sub 1' to 'sub 2', A changes by a factor of 4.
Going from 'sub 1' to 'sub 2', B also changes by a factor of 4.
Both A and B change by the same factor. That factor is 4.
Therefore, A is directly proportional to B.
Again:
This straight line graph really tells two stories. If you can say that A is directly proportional to B, then you can state that B is directly proportional to A. The above works out the same.
The function in the graph used here is:
Or, using formal function definition writing:
Lastly:
If someone says, 'A is proportional to B', they most assuredly mean, 'A is directly proportional to B'. Some might feel that the constant inclusion of the word 'direct' is unnecessary. It does, though, get to exactly what you are talking about, because there are other types of proportions
Answer:
A(3,-5) abscissa:3 ordenada: -5
B(-1,0) abscissa: -1 ordenada: 0
C(-3,5;-2) abscissa: -3.5 ordenada -2
D(0,-1) abscisa: 0 ordenada:- 1
Step-by-step explanation:
What we must take into account is that the abscissa is the value of x and the ordinate is the value of y. There is always a number of the (x,y), that is, the abscissa is the first value and the ordinate is the second value, therefore:
The total is the 100% and that is 27000, the question is what percentage is 4865
We can use a simple rule of three, direct proportion to solve:
27000 ft^3 --------> 100%
4865 ft^3 ---------> x
x =(4865)(100)/27000
x = 18.02
therefore 4865 ft^3 is 18.02% of 27000 <span>ft^3</span>
Answer:
3
Step-by-step explanation:
Let's find the first term in terms of p.
So an arithmetic sequence is a linear relation.
That means it will have the same slope no matter the pair of points used. We are given the slope, the common difference, is 2. We are going to use point (9, 3+3p) and (1, t(1)) along with m=2 to find t(1).
[t(1)-(3+3p)]/[1-9]=2
Simplify denominator
[t(1)-(3+3p)]/[-8]=2
Multiply both sides by -8
t(1)-(3+3p)=-16
Add (3+3p) on both sides
t(1)=-16+3+3p
Combine like terms
t(1)=-13+3p
This means we can find the next term by adding 2 this.
t(2)=-11+3p
Let's find the next term by adding 2 this.
t(3)=-9+3p
Finally we can find the 4th term by adding 2 to this
t(4)=-7+3p
We are given the sum of the first 4 terms is 2p-10. So we can write:
-13+3p+-11+3p+-9+3p+-7+3p=2p-10
Combine like terms on left
12p-40=2p-10
Subtract 2p on both sides
10p-40=-10
Add 40 on both sides
10p=30
Divide both sides by 10
p=3.
-----------------
Checking:
t(1)=-13+3p=-13+3(3)=-13+9=-4
t(2)=-11+3p=-11+3(3)=-11+9=-2
t(3)=-9+3p=-9+3(3)=-9+9=0
t(4)=-7+3p=-7+3(3)=-7+9=2
----sum of the first 4 is -4
And 2p-10 at p=3 gives 2(3)-10=6-10=-4
So this part checks out
In general, the pattern that those 4 terms I wrote out follow t(n)=(-13-2)+2n+3p. I know this because the 0th term would have been (-13-2)+3p and this part goes up by 2 each time. The plus 3p part doesn't change.
Anyways t(9)=(-13-2)+2(9)+3p=-15+18+3p=3+3p. And this part looks good too.
