Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main 20203 SeptemberMorning Shift
Exam
JEE Main
Year
2020
Date
3 September
Shift
Morning Shift
Subject
Mathematics
Chapter
Limits

JEE Main 2020 · 3 September · Morning Shift · Mathematics · Limits

Let [t] denote the greatest integer ≤ t . If λεR - \ 0, 1\ , _ x →...

Let [t]\left[t\right] denote the greatest integer ≤t\le t. If λεR−{0,1},lim⁡x→0∣1−x+∣x∣λ−x+[x]∣=L\lambdaεR - \left\{0, 1\right\}, \lim_{x \to 0}\left|\dfrac{1 - x + \left|x\right|}{\lambda - x + \left[x\right]}\right| = L, then LL is equal to

Options

  1. A11
  2. B22
  3. C12\dfrac{1}{2}
  4. D00

Correct answer

B. 22

Step-by-step solution

lim⁡x→0∣1−x+∣x∣λ−x+[x]∣=L\lim_{x \to 0}\left|\dfrac{1 - x + \left|x\right|}{\lambda - x + \left[x\right]}\right| = L

Let's find left-hand and right-hand limit.

For left-hand limit

x=0−h,x→0,h→0,h>0x = 0 - h, x \to 0, h \to 0, h > 0

LHL=lim⁡h→0∣1−(−h)+∣−h∣λ−(−h)+[−h]∣LHL = \lim_{h \to 0}\left|\dfrac{1 - \left(- h\right) + \left|- h\right|}{\lambda - \left(- h\right) + \left[- h\right]}\right|

⇒LHL=lim⁡h→0∣1+h−(−h)λ+h+[−h]∣⇒ LHL = \lim_{h \to 0}\left|\dfrac{1 + h - \left(- h\right)}{\lambda + h + \left[- h\right]}\right|

Since h>0⇒[−h]=−1h > 0 ⇒ \left[- h\right] = - 1

⇒LHL=lim⁡h→0∣1+h+hλ+h−1∣=1∣λ−1∣⇒ LHL = \lim_{h \to 0}\left|\dfrac{1 + h + h}{\lambda + h - 1}\right| = \dfrac{1}{\left|\lambda - 1\right|}

For right-hand limit

x=0+h,x→0,h→0,h>0x = 0 + h, x \to 0, h \to 0, h > 0

RHL=lim⁡h→0∣1−h+∣h∣λ−h+[h]∣RHL = \lim_{h \to 0}\left|\dfrac{1 - h + \left|h\right|}{\lambda - h + \left[h\right]}\right|

Since h>0⇒[h]=0h > 0 ⇒ \left[h\right] = 0

⇒RHL=lim⁡h→0∣1+h+hλ+h+0∣=1∣λ∣⇒ RHL = \lim_{h \to 0}\left|\dfrac{1 + h + h}{\lambda + h + 0}\right| = \dfrac{1}{\left|\lambda\right|}

For existence of limit LHL=RHLLHL = RHL

⇒1∣λ−1∣=1∣λ∣⇒ \dfrac{1}{\left|\lambda - 1\right|} = \dfrac{1}{\left|\lambda\right|}

Cross multiply and square both side.

⇒λ2=(λ−1)2⇒λ2=λ2+1−2λ⇒ {\lambda}^{2} = {\left(\lambda - 1\right)}^{2} ⇒ {\lambda}^{2} = {\lambda}^{2} + 1 - 2\lambda

⇒λ=12⇒ \lambda = \dfrac{1}{2}

Limit L=112=2L = \dfrac{1}{\dfrac{1}{2}} = 2

Practice Limits on Quantrex Academy →

More from Limits

Let _ x → 2 (( (x-2))(rx^2 + (p-2)x - 2p))/((x-2)^2) = 5 for some r, p ∈ ℝ . If the set… JEE Main 2026The value of _ x → 0 ((x^2 ^2 x)/(x^2 - ^2 x)) is: JEE Main 2026Let f(x) = _ y → 0 ((1 - (xy)) (xy))/(y^3) . Then the number of solutions of the equation… JEE Main 2026The product of all possible values of α , for which _ x → 0 ((1 - (α x) ((α+1)x)… JEE Main 2026If _ x → 2 (x^3 - 5x^2 + ax + b) ( x-1 - 1) _e(x-1) = m , then a + b + m is equal to : JEE Main 2026The value of _ x arrow 0 _ e ( (e x) · (e^ 2 x) · … · (e^ 10 x)) e^ 2 -e^ 2 x is equal to JEE Main 2026If _ x arrow 0 e^ (a-1) x +2 ~b x+(c-2) e^ -x x x- _ e (1+x) =2 , then a^ 2 +b^ 2 +c^ 2… JEE Main 2026Let [·] denote the greatest integer function and f(x)= _ n arrow ∞ 1 n^ 3 ∑_ k=1 ^ n [ k^… JEE Main 2026Let f: R arrow(0, ∞) be a twice differentiable function such that f(3)=18, f^ (3)=0 and… JEE Main 2026Let α and β be the real numbers such that _ x arrow 0 (1)/(x^3)((α)/(2) ∫_0^x (1)/(1-t^2)… JEE Advanced 2025Let x_0 be the real number such that e^ x_0 +x_0=0 . For a given real number α , define… JEE Advanced 2025Given below are two statements : Statement I : _ x arrow 0 ( ^ -1 x+ _e (1+x)/(1-x) -2 x… JEE Main 2025If the function f(x)=( ( x)- ( x))/( x- x) is continuous at x=0 , then f(0) is equal to… JEE Main 2025_ x arrow 0^ + (5(x)^ (1)/(3) ) _e(1+3 x^2) ( ^ -1 3 x )^2(e^ 5(x)^ (4)/(3) -1) is equal… JEE Main 2025If _ x arrow 1^ + ((x-1)(6+λ (x-1))+μ (1-x))/((x-1)^3)=-1 , where λ, μ ∈ ℝ , then λ+μ is… JEE Main 2025If Lim_ x arrow 0 (( x)/(x))^ (1)/(x^2) =p , then 96 _e p is equal to ______ JEE Main 2025 Full Limits list Limits JEE Maths PYQsJEE Mathematics PYQs All JEE Main PYQs