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TextBook Solutions for Mizoram Board Class 12 Mathematics Mathematics Part Ii Chapter 9 Differential Equations

Question 1
CBSEENMA12033080

At any point (x, y) of a curve, the slope of the tangent is twice the slope of the line segment joining the point of contact to the point (– 4, – 3). Find the equation of the curve given that it passes through ( 2, 1).

Solution
Let y = f(x) be equation of curve.
Now dy over dx is the slope of the tangent to the curve at the point (x, y)
From the given condition, 
          dy over dx space equals space 2 open parentheses fraction numerator negative 3 minus straight y over denominator negative 4 minus straight x end fraction close parentheses space space or space space space dy over dx space equals space 2 open parentheses fraction numerator straight y plus 3 over denominator straight x plus 4 end fraction close parentheses
Separating the variables,  we get,
                           fraction numerator 1 over denominator straight y plus 3 end fraction dy space equals space fraction numerator 2 over denominator straight x plus 4 end fraction dx
Integrating, integral fraction numerator 1 over denominator straight y plus 3 end fraction space dy space equals space 2 space integral fraction numerator 1 over denominator straight x plus 4 end fraction dx
therefore space space space log space open vertical bar straight y plus 3 close vertical bar space equals space 2 space log space open vertical bar straight x plus 4 close vertical bar plus straight c                                  ...(1)
Since curve passe through (-2, 1)
WiredFaculty
which is required equation of curve.

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