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4.6 Example Problems

Here are some problems to try:

1. State whether the following equations show direct variation:

Y=56x+0 Y=10x-1

Y=X Y=5x

2. The variables x and y vary directly. When x=12 and y= 3...

a. write an equation relating x and y

b. FInd the value, using the equation in a, of y when x=24

3. What is the slope of the equation Y=5/6x ?

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4.6 Example Answers

1. Y=56x+0 shows direct variation because it says that this line intercepts at the orgin, (0) on the y axis, meaning that it varies directly

Y=10x-1 doesn't vary directly because the y intercept is -1, not 0

Y=X does vary directly because it doesn't have another number added meaning that it could be written as Y=X+0 making the y intercept 0

Y=5x does vary directly because it doesn't have another number added meaning that it could be written as Y=5X+0 making the y intercept 0

2. a. y=1/4x

b. y= 6

3. the slope is 5/6

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