CBSE Class 12 Math 2008 Solved Paper

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Question : 14
Total: 29
For what value of k is the following function continuous at x = 2?
f (x) = {
2x+1x<2
kx=2
3x−1x>2
Solution:  
The given function f(x) will be continuous at x = 2, if
lim
x→2−
f (x) =
lim
x→2+
f (x) = f (2)
lim
x→2−
=
lim
x→2−
2x + 1 = 2 × 2 + 1 = 5
lim
x→2−
=
lim
x→2−
3x + 1 = 3 × 2 - 1 = - 5
∴ f (2) = k
⇒ k = 5
Thus, for k = 5, the given function is continuous at x = 2.
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