Using info from g' and g'' to find answer

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SUMMARY

The discussion focuses on determining a possible value for g(6) given the conditions of a twice differentiable function g, where g'(x) > 0 and g''(x) > 0 for all x. With g(4) = 12 and g(5) = 18, the calculated slope between these points is 6. Since the second derivative is positive, indicating an increasing slope, the only viable option for g(6) is 27, as it maintains the increasing nature of the slope from g(5).

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Homework Statement


Let g be a twice differentiable function with g'(x)>0 and g''(x)>0 for all x.
g(4)=12 and g(5)=18. Which is a possible value for g(6)?

a)15
b)18
c)21
d)24
e)27

Homework Equations


slope=change y/ change x


The Attempt at a Solution


Ok so [g(5)-g(4)]/1=6
a-c is eliminated since they produce slopes less than 6. Since we know g''(x)>0. the slope must be increasing.

if g(6)=24 we get [g(6)-g(5)]/1=6. but this is a problem since the slope must be have increased from 4 to 5. So the answer is e) 27.

Is my reasoning correct?
 
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Yes, you got it.

As an analogy you could look at y=x^3, y'=3x^2 and y''=6x.
 

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