Consider the piecewise function f(x) = (4x^2 -3)/(3x^2-15)  ,   x less than -2          (4-x^2)^(1/2)        ,       -2 less than = to x less than= to 2          5 ,                                 x greater than 2 a) Draw a neat sketch of its graph. b) use algebra to find lim x--> -infinity f(x) c) find the following ; lim x--> (-2)^ - f(x) = ? lim x--> (-2)^+ f(x)= 0 f(-2)= 0 f(4)= 5 And list the values of c for which f(x) is not continuos :

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The function f(x) is defined over three regions.

f(x) =

`(4x^2-3)/(3x^2-15)`            `xlt-2`

`sqrt((4-x^2))`          `-2lt=xlt=2`

`5`                     ` xgt2`


When x goes to `-oo` , the relevant function is the first one, when `xlt-2`


you can't calculate the limit straight away, but you can divide both numerator and denominator from x^2 and modify this expresssion.



Now if we take the limit,

`lim_(x-gt-oo)(4-3/(-oo)^2)/(3-15/(-oo)^2) = (4-0)/(3-0)`


`lim_(x-gt-oo)f(x) = 4/3`



This is the limit when x is approaching to -2 from the negative infinity side. Therefore still the function is the first one,

`lim_(x-gt-2^-)f(x) =` `lim_(x-gt-2^-)[(4x^2-3)/(3x^2-15)] = (4*(-2)^2-3)/(3*(-2)^2-15)`

` ` `lim_(x-gt-2^-)f(x) =13/(-3) = -13/3`



This is the limit when x is approaching to -2 from the positive infinity side(or decreasing to -2). Therefore now the function is the second one.

`lim_(x-gt-2^+)f(x) = lim_(x-gt-2^+)sqrt(4-x^2)`


`lim_(x-gt-2^+)f(x) = 0`


If you have noticed,

`lim_(x-gt-2^-)f(x) != lim_(x-gt-2^+)f(x)`

So at x =-2 , f(x) has a jump discontiuity.

The other discontinuity is at x=2.

So there are discontinuities at x =-2 and x =2.


`f(-2) = sqrt(4-(-4)^2) = 0`

`f(4) = 5` (since 4>2)



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