Which of the following best represents the direction field for the differential equation
$$\frac{dy}{dx} = -\frac{x}{4y}$$
A - HSC - SSCE Mathematics Extension 1 - Question 7 - 2020 - Paper 1
Question 7
Which of the following best represents the direction field for the differential equation
$$\frac{dy}{dx} = -\frac{x}{4y}$$
A.
B.
C.
D.
Worked Solution & Example Answer:Which of the following best represents the direction field for the differential equation
$$\frac{dy}{dx} = -\frac{x}{4y}$$
A - HSC - SSCE Mathematics Extension 1 - Question 7 - 2020 - Paper 1
Step 1
Identify the differential equation
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Answer
The given differential equation is dxdy=−4yx. This represents how the slope of the solution curve varies based on the values of x and y.
Step 2
Determine the characteristics of the direction field
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Answer
To analyze the direction field, we note that it indicates the slope of the solution at each point in the (x,y) plane. Specifically, the slope is negative for positive values of y and positive for negative values of y. This suggests that as x increases, y will decrease when y>0 and increase when y<0.
Step 3
Eliminate incorrect options
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Answer
Options B, C, and D can be ruled out because they do not conform to the behavior described above: they either have the wrong orientation or create inconsistencies in the expected slope behavior.
Step 4
Select the correct direction field
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Answer
The correct representation of the direction field that matches the behavior of the solution to the given differential equation is option A.