NIMCET 2023 — Mathematics PYQ
NIMCET | Mathematics | 2023lf is a real number then

lf f(x)=limx→0loge9(1−cosx)6x−3x−2x+1 is a real number then limx→0f(x)
2
3
Loge2
(Correct Answer)Loge3
Loge2
Let's consider the expression inside the limit:
L=x→0limloge9(1−cosx)6x−3x−2x+1
First, factorize the numerator by grouping the terms:
6x−3x−2x+1=(2⋅3)x−3x−2x+1
=2x⋅3x−3x−2x+1
=3x(2x−1)−1(2x−1)
=(3x−1)(2x−1)
Now substitute this back into the limit expression:
L=x→0limloge9(1−cosx)(3x−1)(2x−1)
We will utilize the following standard limit properties as x→0:
limx→0xax−1=logea
limx→0x21−cosx=21
To use these standard forms, let's divide both the numerator and the denominator by x2:
L=loge91⋅x→0limx21−cosxx2(3x−1)(2x−1)
Separate the terms in the numerator:
L=loge91⋅limx→0x21−cosx(limx→0x3x−1)⋅(limx→0x2x−1)
Substitute the values from the standard limit properties:
limx→0x3x−1=loge3
limx→0x2x−1=loge2
limx→0x21−cosx=21
Putting it all together:
L=loge91⋅21(loge3)⋅(loge2)
We know that loge9=loge(32)=2loge3. Substituting this into the denominator:
L=2loge31⋅21(loge3)⋅(loge2)
Cancel out loge3 from the numerator and denominator:
L=2⋅21loge2
L=loge2
Correct Option: C
Let's consider the expression inside the limit:
L=x→0limloge9(1−cosx)6x−3x−2x+1
First, factorize the numerator by grouping the terms:
6x−3x−2x+1=(2⋅3)x−3x−2x+1
=2x⋅3x−3x−2x+1
=3x(2x−1)−1(2x−1)
=(3x−1)(2x−1)
Now substitute this back into the limit expression:
L=x→0limloge9(1−cosx)(3x−1)(2x−1)
We will utilize the following standard limit properties as x→0:
limx→0xax−1=logea
limx→0x21−cosx=21
To use these standard forms, let's divide both the numerator and the denominator by x2:
L=loge91⋅x→0limx21−cosxx2(3x−1)(2x−1)
Separate the terms in the numerator:
L=loge91⋅limx→0x21−cosx(limx→0x3x−1)⋅(limx→0x2x−1)
Substitute the values from the standard limit properties:
limx→0x3x−1=loge3
limx→0x2x−1=loge2
limx→0x21−cosx=21
Putting it all together:
L=loge91⋅21(loge3)⋅(loge2)
We know that loge9=loge(32)=2loge3. Substituting this into the denominator:
L=2loge31⋅21(loge3)⋅(loge2)
Cancel out loge3 from the numerator and denominator:
L=2⋅21loge2
L=loge2
Correct Option: C