1.

Form a differential equation representing the given family of curves by eliminating arbitrary constant a and b.y = ae3x + be-2x

Answer»

y = a e3x + b e-2x ….(1) 

Differentiating w.r.t x , y, = ae3x.3 + be2x (-2) ….(2) 

multiply (1) by 3 

⇒ 3y = 3ae3x + 3be-2x 

⇒ 3ae3x = 3y -3be-2x …(3) 

put (3) in (2), we get y, = 3y – 3be-2x – 2be-2x 

⇒ y – 3y = -5 be-2x …….. (4) 

differentiating again ⇒ y2 – 3y1 = -5be-2x (-2) ….(5) 

multiply (4) by 2, we get 

⇒ 2y,- 6y = -10be2x ….(6) 

putting (6) in (5), we get 

⇒ -(2y1 – 6y) = y2 -3y1 

⇒ y2 – 3y1 + 2(y1 3y) = 0 

⇒ y2 -y1 – 6y = 0 is the required differential equation.



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