Suneil P. answered • 06/20/14

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Jessica S.

asked • 06/20/14Let f(x)=(7x-2)/(x+2). Find the open intervals on which f is concave up (down). Then determine the x-coordiantes of all inflection points of f.

1. f is concave up on these intervals?=

2. f is concave down on these intervals?

3. the inflection points occur at x=?

PLEASE PROVIDE FINAL ANWERS.

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Suneil P. answered • 06/20/14

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I Believe I Answered This.

James F. answered • 06/20/14

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First, take f'(x) = 16/(x+2)^2 using the quotient rule

Next, take f''(x) = -32/(x+2)^2 using the quotient rule on the first derivative

Solving f''(x) = 0 would normally give the point of inflection, but in this case we'll get no solution, so we will inspect the critical value of x = -2.

Next, check a value smaller than x = -2 and a value larger than x = -2 to test for concavity (negative implies concave down).

Let me know if this gets you going in the right direction!

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