Q. 205.0( 2 Votes )

# Let . If f(x) is continuous at find a and b.  (CBSE 2016)

Answer :

Given:

f(x) is continuous at x = & f() = a,

If f(x) to be continuous at x = ,we have to show, f() = f() + = f()

LHL = f() =

sin(–x) = cosx

cos(–x) = sinx

(a3–b3) = (a–b)(a2 + ab + b2)

cos(0) = 1

...(1)

LHL = f() + =

1

...(2)

f(x) is continuous at x = & f() = a ,and from (1) & (2),we get

f() = f() + = f()

= a

a =

b = 4

Hence ,a = & b = 4

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