Suppose y is directly proportinal to x

  • Thread starter mech-eng
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In summary, the given information states that y is directly proportional to x, and this can be represented by the equation y = ax, where a is a constant. Using this information, we can show that y is a linear function of x, with a slope of 0.04 for the first line and 0.067 for the second line. The concept of proportionality is important in understanding the relationship between x and y, where doubling the value of x doubles the value of y.
  • #1
mech-eng
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Homework Statement


upload_2017-5-5_12-33-17.jpeg
[/B]

Suppose that y is directly proportional to x. Show that y is a linear function of x. Both lines goes through the origin. First line goes 1250 ft in x direction and 50 ft in y direction. The second line goes 13740 ft in x direction and 920.58 ft in y direction.

Source: Algebra and Trigonometry by Keedy/Bittinger.

Homework Equations


y=mx+n[/B]

The Attempt at a Solution



1.y=mx+n since line goes through the origin y-intercept is 0. We know y-intercept and slope then we can write a slope-intercept equation for the line. m=50/1250=0.04; y=0.04x

2. y=mx+n since line goes through the origin y-intercept is 0. We know y-intercept and slope then we can write a slope-intercept equation for the line. m=0.067x

But here I do not understand why the information "y is directly proportional to x" is given? What are other ways to solve this problem?

Thank you.

[/B]
 
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  • #2
mech-eng said:
But here I do not understand why the information "y is directly proportional to x" is given? What are other ways to solve this problem?
Its given cause its implies x is proportional to y. Like y=ax where a is a constant reel number this function like y=ax so f(x)=ax is a linear function.I don't think there's any other way to solve this question.
 
  • #3
Isn't y in y=x2directly proportinal to x?
 
  • #4
mech-eng said:
Isn't y in y=x2directly proportinal to x?
Its not
 
  • #5
If y is directly proportional to x, then doubling the value of x doubles the value of y.
 
  • #6
DrClaude said:
If y is directly proportional to x, then doubling the value of x doubles the value of y.
How is this square case of proportionality called?

Thank you.
 
  • #7
mech-eng said:
How is this square case of proportionality called?
"y is proportional to x squared"

Mathematically, it is the difference between ##y \propto x## and ##y \propto x^2##.
 
  • #8
mech-eng said:
How is this square case of proportionality called?

Thank you.

##y## proportional to ##f(x)## just means that ##y/f(x)## is a constant; that is, ##y = c f(x)## for some constant ##c##.
 
  • #9
What's with the question numbers (50,51,52)? Is 50 referring to 51 and 52?
 
  • #10
CWatters said:
What's with the question numbers (50,51,52)? Is 50 referring to 51 and 52?

I think 50 is the question and 51 and 52 are parts of it. That's all in the picture.

Thank you.
 

FAQ: Suppose y is directly proportinal to x

What does it mean for y to be directly proportional to x?

When two variables, y and x, are directly proportional, it means that as the value of x increases, the value of y also increases at a constant rate. Similarly, as the value of x decreases, the value of y also decreases at the same constant rate.

How can I recognize a direct proportionality between y and x?

A direct proportionality between y and x can be recognized by plotting the values of y and x on a graph and observing a straight line passing through the origin (0,0). The slope of this line represents the constant rate at which y changes with respect to x.

What is the formula for calculating direct proportionality between y and x?

The formula for calculating direct proportionality between y and x is y = kx, where k represents the constant of proportionality.

Can the constant of proportionality, k, ever be equal to 0?

No, the constant of proportionality, k, cannot be equal to 0 because this would mean that y is not dependent on x and there is no direct relationship between the two variables.

How can I use direct proportionality to solve real-world problems?

Direct proportionality can be used to solve real-world problems by setting up a proportion between two related quantities and using the constant of proportionality to calculate the unknown value. For example, if it takes 2 hours to drive 100 miles, we can set up the proportion 2 hours / 100 miles = x hours / 200 miles to find the time it would take to drive 200 miles at the same constant rate.

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