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Evaluate the following: limx→0[3x+3-x-2x2]

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Question

Evaluate the following: `lim_(x -> 0) [(3^x + 3^-x - 2)/x^2]`

Sum
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Solution

`lim_(x -> 0) (3^x + 3^-x - 2)/x^2`

= `lim_(x -> 0) (3^x + 1/3^x - 2)/x^2`

= `lim_(x -> 0) ((3^x)^2 + 1 - 2(3^x))/(3^x*x^2)`

= `lim_(x -> 0) ((3^x - 1)^2)/(x^2*(3^x)`   ...[∵ a2 – 2ab + b2 = (a – b)2]

= `lim_(x -> 0)((3^x - 1)/x)^2 xx 1/3^x`

= `lim_(x -> 0) ((3^x - 1)/x)^2 xx 1/(lim_(x -> 0) (3^x)`

= `(log3)^2 xx 1/3^0`

= `(log3)^2 xx 1/1   ....[lim_(x -> 0) ("a"^x - 1)/x = log "a"]`

= (log3)2 

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Chapter 7: Limits - EXERCISE 7.4 [Page 105]

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