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Complete the table below to show the values of $V(x) = 4x^3 - 40x^2 + 100x$, where $x \in \mathbb{R}$, for the given values of $x$ in the domain $0 \leq x \leq 5$ - Leaving Cert Mathematics - Question d, e, f - 2021

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Question d, e, f

Complete-the-table-below-to-show-the-values-of-$V(x)-=-4x^3---40x^2-+-100x$,-where-$x-\in-\mathbb{R}$,-for-the-given-values-of-$x$-in-the-domain-$0-\leq-x-\leq-5$-Leaving Cert Mathematics-Question d, e, f-2021.png

Complete the table below to show the values of $V(x) = 4x^3 - 40x^2 + 100x$, where $x \in \mathbb{R}$, for the given values of $x$ in the domain $0 \leq x \leq 5$. ... show full transcript

Worked Solution & Example Answer:Complete the table below to show the values of $V(x) = 4x^3 - 40x^2 + 100x$, where $x \in \mathbb{R}$, for the given values of $x$ in the domain $0 \leq x \leq 5$ - Leaving Cert Mathematics - Question d, e, f - 2021

Step 1

Complete the table for $V(x)$

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Answer

To find the values of V(x)V(x), we will substitute each xx value into the equation:

  1. For x=0x = 0:
    V(0)=4(0)340(0)2+100(0)=0V(0)=40V(0) = 4(0)^3 - 40(0)^2 + 100(0) = 0 \Rightarrow V(0) = 40

  2. For x=0.5x = 0.5:
    V(0.5)=4(0.5)340(0.5)2+100(0.5)=4(0.125)40(0.25)+50=0.510+50=40V(0.5)=64V(0.5) = 4(0.5)^3 - 40(0.5)^2 + 100(0.5) = 4(0.125) - 40(0.25) + 50 = 0.5 - 10 + 50 = 40 \Rightarrow V(0.5) = 64

Continue in the same manner for x=1,1.5,2,2.5,3,3.5,4,4.5,5x = 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 to complete the table.

Step 2

Draw the graph of the function $V(x)$

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Answer

Plot the points from the completed table on the grid. Connect the points smoothly to represent the continuous nature of the function. The graph should reach a peak at the maximum volume and then decline.

Step 3

(i) The maximum volume of the box.

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Answer

Analyzing the graph, the maximum volume occurs at the vertex of the parabola, estimated at approximately V(x)=74V(x) = 74.

Step 4

(ii) The values of $x$ which will create a box which has a volume of 30 units cubed.

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Answer

From the graph, the values of xx that intersect with the line V(x)=30V(x) = 30 are approximately x=0.35x = 0.35 and x=3.55x = 3.55.

Step 5

(iii) The volume of the box when $x = 2$ units.

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Answer

Substituting x=2x = 2 into the volume function: V(2)=4(2)340(2)2+100(2)=32160+200=72V(2)=72.V(2) = 4(2)^3 - 40(2)^2 + 100(2) = 32 - 160 + 200 = 72 \Rightarrow V(2) = 72.

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