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TS EAMCET · Maths · Differential Equations

If \(\quad d x+d y=(x+y)(d x-d y), \quad\) then \(\log (x+y)\) is equal to

  1. A \(x+y+c\)
  2. B \(x+2y+c\)
  3. C \(x-y+c\)
  4. D \(2 x+y+c\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(x-y+c\)

Step-by-step Solution

Detailed explanation

Given that \(d x+d y=(x+y)(d x-d y)\) \(\Rightarrow \quad d x(x+y-1)=d y(x+y+1)\) \(\Rightarrow \quad \frac{d y}{d x}=\frac{x+y-1}{x+y+1}\) ...(i) Let \(x+y=t\) \(\Rightarrow \quad \frac{d y}{d x}=\frac{d t}{d x}-1\) \(\therefore\) From Eq. (i)…