1
limx→1x4−1x−1=limx→kx3−k2x2−k2=, then find k
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Solution
Quick DL Method Solution
Given:
limx→1x4−1x−1=limx→kx3−k2x2−k2
LHS using derivative:
limx→1x4−1x−1=ddx(x4)|x=1=4x3|x=1=4
RHS using DL logic:
limx→kx3−k2x2−k2≈3k2(x−k)2k(x−k)=3k2
Equating both sides:
3k2=4⇒k=83
k=83
3
Let f(x)=x2−1|x|−1. Then the value of limx→−1f(x) is
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Solution
4
The value of the limit
limx→0(1x+2x+3x+4x4)1/x
is
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Solution
4
Which of the following is NOT true?
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4
For a∈R (the set of al real numbers), a≠1, limn→∞(1a+2a+…+na)(n+1)a−1[(na+1)(na+b)…(na+n)]=160 . Then one of the value of a is
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3
The value of Ltx→0ex−e−x−2x1−cosx is equal to
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Solution
Evaluate:
limx→0ex−e−x−2x1−cosx
Step 1: Apply L'Hôpital's Rule (since it's 0/0):
First derivative:
ex+e−x−2sinx
Still 0/0 → Apply L'Hôpital's Rule again:
ex−e−xcosx
Now,
limx→01−11=0
Final Answer:
0
1
Let f(x) be a polynomial of degree four, having extreme value at x = 1 and x = 2. If limx→0[1+f(x)x2]=3, then f(2) is
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Solution
Given it has extremum values at x=1 and x=2
⇒f′(1)=0 and f′(2)=0
Given f(x) is a fourth degree polynomial
Let
f(x)=ax4+bx3+cx2+dx+eGiven
limx→0[1+f(x)x2]=3
limx→0[1+ax4+bx3+cx2+dx+ex2]=3
limx→0[1+ax2+bx+c+dx+ex2]=3
For limit to have finite value, value of 'd' and 'e' must be 0
⇒d=0 & e=0
Substituting x=0 in limit
⇒ c+1=3
⇒ c=2
f′(x)=4ax3+3bx2+2cx+d
x=1 and x=2 are extreme values,
⇒f′(1)=0 and $f^{\prime}(2)=0
⇒ 4a+3b+4=0 and 32a+12b+8=0
By solving these equations
we get, a=12 and b=−2
So,
f(x)=x42−2x3+2x2
⇒f(x)=x2(x22−2x+2)
⇒f(2)=0
4
The value of limx→a√a+2x−√3x√3a+x−2√x
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Solution
4
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Solution
Function is the form of

therefore using by L'Hospital rule
=

Again apply L'Hospital Rule,
=

Putting x = 0, we get
2
Find

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Solution
3
If f(x)=limx→06x−3x−2x+1loge9(1−cosx) is a real number then limx→0f(x)
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Solution
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