Q.
Column I contains functions and column II contains their natural domains. Exactly one entry of
column II matches with exactly one entry of column I.
Column I
Column II
A
f(x)=sin−1(xx+1)
P
(1,3)∪(3,∞)
B
g(x)=ln(x+1x2+3x−2)
Q
(−∞,2)
C
h(x)=ln(2x−1)1
R
(−∞,−21]
D
ϕ(x)=ln(x2+12−2x)
S
[−3,−1)∪[1,∞)
176
150
Relations and Functions - Part 2
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Solution:
(A)f(x)=sin−1(xx+1);−1≤xx+1≤1 ∴xx+1−1≤0;x1≤0⇒x<0 and 0≤1+xx+1;0≤x2x+1⇒x2x+1≥0
Hence domain of f(x) is (−∞,−21]
(B)lnx+1x2+3x−2≥0;x+1x2+3x−2≥1;x+1x2+3x−2−x−1≥0;x+1x2+2x−3≥0 x+1(x+3)(x−1)≥0
hence ⇒ (S)
(C)ln(2x−1)=0⇒2x−1=1⇒x=3
also 2x−1>0⇒x>1 (1,∞)−{3}⇒
(D) for x≤0,x2+12>2x always true for x>0x2+12>4x2 0>3x2−12⇒x2−4<0 ∴x∈(0,2)⇒domain(−∞,2)⇒ (Q) ]