Based on the given variation, y does not vary directly with x and the constant of variation are 8, 3.2 and 1.25 respectively.
<h3>Variation</h3>
y = k × x
where,
k = constant of proportionality
y = -40
x = -5
y = k × x
-40 = k × -5
-40 = -5k
k = -40/-5
k = 8
when,
y = 8 and x = 2.5
y = k × x
8 = k × 2.5
8 = 2.5k
k = 8/2.5
k = 3.2
when,
y = 5 and x = 4
y = k × x
5 = k × 4
5 = 4k
k = 5/4
k = 1.25
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Answer:

Step-by-step explanation:
Given


Required
Determine the equation in slope intercept form
First, we calculate the slope of the line:

This gives:




Th equation is then calculated using:

This gives:

Open bracket

Make y the subject


Answer:

Step-by-step explanation:
Here it is mentioned that the there are two concentric circles this means that they have the same center.
The center of the circles are the origin
.
Radius of the outer circle is

Equation of a circle

where


Here the equation will be

The equation of the outer circle is 
Answer:
5^15
Step-by-step explanation:
When the bases are the same, we add the exponents when multiplying
5^10 * 5^5
5^(10+5)
5^15
Answer:
78732
Step-by-step explanation: