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Question

lxl+3, if xs-3-2x.6x2, if x237.f(x)-i

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Solution

The given function is,

f( x )={ | x |+3,x3 2x,3<x<3 6x+2,x3

Consider k be any real number, then the cases will be k<3, k=3, 3<k<3, k>3 or k=3.

When k<3, the function becomes,

f( k )=k+3

The limit of the function is,

lim xk f( x )= lim xk ( x+3 ) =k+3

It can be observed that, lim xk f( x )=f( k ).

Therefore, the function is continuous for all real numbers less than 3.

When k=3, the left hand limit of the function is,

LHL= lim x 3 f( x ) = lim x 3 ( x+3 ) =( 3 )+3 =6

The right hand limit of the function at k=3 is,

RHL= lim x 3 + f( x ) = lim x 3 + ( 2x ) =( 2 )( 3 ) =6

It can be observed that, LHL=RHL.

Therefore, the function is continuous at x=3.

When 3<k<3, the function becomes,

f( k )=2k

The limit of the function is,

lim xk f( x )= lim xk ( 2x ) =2k

It can be observed that, lim xk f( x )=f( k ).

Therefore, the function is continuous in 3<k<3.

When k=3, the left hand limit of the function is,

LHL= lim x 3 f( x ) = lim x 3 ( 2x ) =6

The right hand side of the function at k=3 is,

RHL= lim x 3 + ( 6x+2 ) =6( 3 )+2 =20

It can be observed that, LHLRHL.

Therefore, the function is discontinuous at x=3.

When k>3, the function becomes,

f( k )=6k+2

The limit of the function is,

lim xk f( x )= lim xk ( 6x+2 ) =6k+2

It can be observed that lim xk f( x )=f( k ).

Therefore, the function is continuous for all numbers greater than 3.


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