NCERT Class XI Mathematics - Limits and Derivatives - Solutions

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Question : 23
Total: 72
Find
lim
x0
f (x) and
lim
x1
f (x), where
f (x) = {
2x3x0
3(x+1)x>0
Solution:  
We have, f (x) = {
2x3x0
3(x+1)x>0

For
lim
x0
f (x) , we have to evaluate
lim
x0
f (x) and
lim
x0+
f (x) separately as f(x) is defined differently on left and right of 0.
Now,
lim
x0
f (x) =
lim
x0
(2x + 3) = 2 . (0) + 3 = 3
and
lim
x0+
f (x) =
lim
x0+
3 (x + 1) = 3 (0 + 1) = 3.
Thus we see,
lim
x0
f (x) =
lim
x0+
f (x) = 3
lim
x0
f (x) = 3
Now,
lim
x1
f (x) 3 (x + 1) = 3 × 2 = 6
lim
x1
f (x) = 6 and
lim
x0
f (x) = 3.
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