Question 9
The point (30,15) means that x = 30 and y = 15 pair up together.
Similarly, (40,25) means we have x = 40 and y = 25 paired up.
Apply the slope formula to get
m = (y2-y1)/(x2-x1)
m = (25-15)/(40-30)
m = 10/10
m = 1
The slope is 1.
It tells us that each time y goes up by 1, x is also increasing by 1.
slope = rise/run = 1/1
rise = 1, run = 1
The rise is the change in y, the run is the change in x.
This means the plant's height (y) goes up by 1 cm each time the number of days (x) goes up by 1.
In short, the plant's height is increasing by 1 cm per day
<h3>
Answer: Choice D</h3>
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Question 10
y varies directly with x, so y = kx for some constant k.
We're then told that x = -1 and y = -2 pair up together.
Let's find k based on those items
y = kx
y/x = k
k = y/x
k = -2/(-1)
k = 2
So y = kx becomes y = 2x
Then we're asked to find x when y = -4
y = 2x
y/2 = x
x = y/2
x = -4/2
x = -2
<h3>
Answer: Choice D</h3>
