Wednesday, February 10, 2016

Can someone please help me answering those problems on the attached files at the bottom?

You are not allowed to ask multiple questions. This is a response for 3 of the several that you have posted.


# If `f(x) = sqrt(x+2)` , determine whether f is continuous from the left, from the right or neither for x = -2


`lim_(x->-2^+) f(x)`


= `lim_(x->-2^+) sqrt(x+2)`


= `sqrt(-2+2)`


= 0


`lim_(x->-2^-) f(x)`


= `lim_(x->-2^-) sqrt(x+2)`


But for x < -2, `sqrt(x+2)` is not real as x + 2 is negative and the square root of a negative number is not real.


Therefore `lim_(x->-2^-) f(x) != f(-2)` .


The function is continuous from the right at x = -2.



# If f and g are continuous with f(3) = 5 and `lim_(x->3)[2*f(x) - g(x)] = 4` , find g(3).


Both the functions f and g are continuous at x = 3.


` lim_(x->3)[2*f(x) - g(x)] = 4`


`=> [2*f(3) - g(3)] = 4`


`=> 2*5 - g(3) = 4`


`=> 10 - g(3) = 4`


`=> g(3) = 10 - 4`


`=> g(3) = 6`


# Use the definition of continuity and the properties of limits to show that the function `f(x) = (x+1)/(2x^2 - 1)` is continuous at x = 4


The value of f(x) at x = 4 is `(4+1)/(2*4^2 - 1) = 5/31`


`lim_(x->4^-)(x+1)/(2x^2 - 1)`


= `5/31`


`lim_(x->4^+)(x+1)/(2x^2 - 1)`


= `5/31`


As for a = 4, `lim_(x->a^-) = lim_(x->a^+) = f(a)` , the function is continuous at x = 4.


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