If y = cosxcosxcosx, then dydx =&nb

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 Multiple Choice QuestionsMultiple Choice Questions

21.

What are the degree and order respectively of the differential equation

y = xdydx2 + dxdy2 ? 

  • 1, 2

  • 2, 1

  • 1, 4

  • 4, 1


22.

What is the differential equation corresponding to y2 - 2ay + x2 = a2 by eliminating a2 ? where p = dydx

  • x2 - 2y2p2 - 4pxy - x2 = 0

  • x2 - 2y2p2 + 4pxy - x2 = 0

  • x2 + 2y2p2 - 4pxy - x2 = 0

  • x2 + 2y2p2 - 4pxy + x2 = 0


23.

What is the general solution to the differential equation

ydx - (x + 2y2)dy = 0 ? 

  • x = y2 + cy

  • x = 2cy2

  • x = 2y2 + cy

  • None of the above


24.

Let f(x + y) = f(0)f(y) for all x and y. Then what is f'(5) equal to [where f'(x) is the derivative of f(x)] ?

  • f5f'(0)

  • f(5) - f'(0)

  • f5f0

  • f5 +f'(0)


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25.

If y = cosxcosxcosx, then dydx = ?

  • - y2tanx1 - ylncosx

  • y2tanx1 + ylncosx

  • y2tanx1 - ylnsinx

  • y2tanx1 + ylnsinx


A.

- y2tanx1 - ylncosx

Let        y = cosxy logy = ylogcosxDifferentiating both sides,      1ydydx = y .  - tanx + logcosx . dydx 1y - logcosxdydx = - ytanx                             dydx =  - y2tanx1 - ylogcosx


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26.

If l1 = ddxesinxl2 = limh0esinx + h - esinxhl3 = esinxcosxdxthen which one of the following is correct ?

  • l1  l2

  • ddxl3 = l2

  • l3dx = l2

  • l2 = l3


27.

The general solution of

dydx = ax + hby + krepresents a circle only when

  • a = b = 0

  • a = - b  0

  • a = b  0, h = k

  • a = b  0


28.

The order and degree of the differential equation

1 + dydx23 = ρ2d2ydx22 are respectively :

  • 3 and 2

  • 2 and 2

  • 2 and 3

  • 1 and 3


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29.

If y = cos-12x1 + x2, Then dydx = ?

  •  - 21 + x2 for all x < 1

  •  - 21 + x2 for all x > 1

  • 21 + x2 for all x < 1

  • None of the above


30.

The differential equation of minimum order by eliminating the arbitrary constants A and C in the equation y = A[sin (x + C) + cos(x + C)] is :

  • y'' + (sin(x) + cos(x))y' = 1

  • y'' = (sin(x) + cos(x))y'

  • y'' = (y')2 + (sin(x)cos(x))

  • y'' + y = 0


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