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Is this a direct variation

y=2x + 3

pls give an explanation if you don’t have one still pls give an answer

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4 votes

Answer:

No.

Explanation:

y/x has to be the same number no matter what except at point (0 0) which it must also include for it to be a direct variation.

*y=2x+3 is not a direct variation because you can not write it as y/x=k where k is some constant number. If we were y=2x, then yes since y/x=2.

*You could also take two points and see if they are proportional. That is, you can see if y2/x2 gives the same value as y1/x1 where (x1,y1) and (x2,y2) are points on the line y=2x+3. This must work for every pair of points on the linear relation except at x=0 (where you would or should have y=0 if it is directly proportional).

Let's try it out. If x=1, then y=2(1)+3=5.

5/1=5

If x=2, then y=2(2)+3=7

7/2=3.5

As you can see 5 doesn't equal 3.5.

*For it to be a direct variation, it also must contain the point (0,0) and be a diagonal line when graphed. It can also be written in form y=kx where k is a constant number. This fails two of the the things I mentioned. It doesn't contain point (0,0) because y=2(0)+3=3 not 0. It cannot be written in form y=kx because of the plus 3.

If it were y=2x, then the answer would be yes.

User Tom Teman
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