Q 21 :    

Let f:R{0}R be a function such that f(x)6f(1x)=353x52. If the limx0(1αx+f(x))=β; α,βR, than α+2β is equal to          [2025]

  • 4

     

  • 3

     

  • 5

     

  • 6

     

(1)

We have, f(x)6f(1x)=353x52           ... (i)

Apply x1x, then

f(1x)6f(x)=35x352           ... (ii)

Using (i) and (ii), we get f(x)=2x13x+12

Now, β=limx0(1αx+f(x))

=limx0(1αx2x13x+12)

=[limx01x(1α13)]+12  α=3, β=12

Hence, α+2β=3+2×12=4



Q 22 :    

The value of limn(k=1nk3+6k2+11k+5(k+3)!) is :          [2025]

  • 5/3

     

  • 4/3

     

  • 7/3

     

  • 2

     

(1)

limn[k=1nk3+6k2+11k+5(k+3)!]

=limn[k=1nk3+6k2+11k+61(k+3)!]

=limn[k=1n(k+3)(k+2)(k+1)1(k+3)!]

=limn[k=1n(1k!1(k+3)!)]

=limn[11!14!+12!15!+13!-16!+14!17!+...+1n!1(n+3)!]

=1+12!+13!=53.

 



Q 23 :    

If limx0(tan xx)1x2=p, then 96logep is equal to __________.          [2025]



(32)

Given, p=limx0(tan xx)1x2

 p=elimx0(tan xxx3)

=elimx0(x+x33+2x55+...xx3)

            [ For 1 form limits, limxaf(x)g(x)=elimxa(f(x)1)g(x)]

=e1/3

  96logep=96×13=32



Q 24 :    

For t > –1, let αt and βt be the roots of the equation ((t+2)1/71)x2+((t+2)1/61)x+((t+2)1/211)=0. If limt1+αt=a and limt1+βt=b, then 72(a+b)2 is equal to __________.          [2025]



(98)

a+b=limt1+(αt+βt)

=limt1+[(t+2)161](t+2)171          [Sum of roots]

Let t + 2 = y, we get

a+b=limy1+y1/61y1/71=-76

So, 72(a+b)2=72(4936)=98.



Q 25 :    

Let f(x)=limnr=0n(tan(x/2r+1)+tan3(x/2r+1)1tan2(x/2r+1)). Then limx0exef(x)(xf(x)) is equal to __________.          [2025]



(1)

We have,

=limn r=0n[2 tan(x2r+1)tan(x2r+1)+tan3(x2r+1)1tan2(x2r+1)]

=limn r=0n[2 tan(x2r+1)1tan2(x2r+1)tan(x2r+1){1tan2(x2r+1)}{1tan2(x2r+1)}]

=limn r=0n(tanx2rtan(x2r+1))=tan x

Now, limx0(exetan xxtan x)

=limx0etan x(extan x1)(xtan x)=1          [ limy0ey1y=1]



Q 26 :    

Let [t] be the greatest integer less than or equal to t. Then the least value of pN for which limx0+(x([1x]+[2x]+...+[px])x2([1x2]+[22x2]+...+[92x2]))1 is equal to _________.          [2025]



(24)

We have,

limx0+(x([1x]+[2x]+...+[px])x2([1x2]+[22x2]+...+[92x2]))1

 (1+2+...+p)(12+22+...+92)1

 p(p+1)29.10.1961

 p(p+1)572 p24.