Problem

Let's consider the function f(x)=2x39x2+12x3. Find the intervals of concavity and the inflection points.

Answer

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Answer

The inflection point is then at x=1.5, and we find the corresponding y-value by substituting x=1.5 into the original function: f(1.5)=2(1.5)39(1.5)2+12(1.5)3=1.125. Therefore, the inflection point is (1.5,1.125)

Steps

Step 1 :First, we find the first derivative of the function: f(x)=6x218x+12

Step 2 :Then, we find the second derivative of the function: f(x)=12x18

Step 3 :Set the second derivative equal to zero and solve for x: 12x18=0 which gives x=1.5

Step 4 :To find the intervals of concavity, we test the sign of the second derivative on each interval. Choose test points x=1 and x=2. For x=1, f(1)=6<0, so the function is concave down on the interval (,1.5). For x=2, f(2)=6>0, so the function is concave up on the interval (1.5,)

Step 5 :The inflection point is then at x=1.5, and we find the corresponding y-value by substituting x=1.5 into the original function: f(1.5)=2(1.5)39(1.5)2+12(1.5)3=1.125. Therefore, the inflection point is (1.5,1.125)

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