Question

The limit  p = lim x π ( x 2 + α x + 2 π 2 x π + 2 sin x ) has a finite value for a real α. The value of α and the corresponding limit p are

Options :

  1. α = −3π, and p = π

  2. α = −2π, and p = 2π

  3. α = π, and p = π

  4. α = 2π, and p = 3π

Show Answer

Answer :

α = −3π, and p = π

Solution :

p = lim x π ( x 2 + α x + 2 π 2 x π + 2 sin x )

substitue x = π

, sin π = 0 We can see that denominator becomes zero.

Thus for p to have finite value numerator is also zero.

π2 + απ + 2π2 = 0

α = - 3π

Now, p = ( π 2 + α π + 2 π 2 π π + 2 sin π ) = 0 0 form

Using L'Hospital's rule, we get

p = lim x π ( 2 x   +   α 1   +   2 cos x )

substituting x = π, α = - 3π

p = ( 2 π     3 π 1   +   2 cos π )

p =  π 1

p = Π

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