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Solve the following differential equation: x dx + 2y dx = 0, when x = 2, y = 1

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Question

Solve the following differential equation:

x dx + 2y dx = 0, when x = 2, y = 1

Sum
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Solution

x dx + 2y dx = 0

∴ x dy = - 2y dx

∴ `1/"y" "dy" = (- 2)/"x" "dx"`

Integrating, we get

`int 1/"y" "dy" = - 2 int 1/"x" "dx"`

∴ log |y| = - 2 log |x| + log c

∴ log |y| = - log |x2| + log c

∴ log |y| = log `|"c"/"x"^2|`

∴ y = `"c"/"x"^2`

∴ x2y = c

This is the general solution.

When x = 2, y = 1, we get

4(1) = c

∴ c = 4

∴ the particular solution is

x2y = 4.

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Notes

The answer in the textbook is incorrect.

  Is there an error in this question or solution?
Chapter 6: Differential Equations - Exercise 6.4 [Page 203]

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