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The table in Part (a)(ii) below shows some of the values of the function: $$h(x) = 0.001x^3 - 0.12x^2 + px + 5, \, x \in \mathbb{R}$$ in the domain $$0 \leq x \leq 75$$ - Leaving Cert Mathematics - Question 8(a) - 2021

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Question 8(a)

The-table-in-Part-(a)(ii)-below-shows-some-of-the-values-of-the-function:--$$h(x)-=-0.001x^3---0.12x^2-+-px-+-5,-\,-x-\in-\mathbb{R}$$--in-the-domain-$$0-\leq-x-\leq-75$$-Leaving Cert Mathematics-Question 8(a)-2021.png

The table in Part (a)(ii) below shows some of the values of the function: $$h(x) = 0.001x^3 - 0.12x^2 + px + 5, \, x \in \mathbb{R}$$ in the domain $$0 \leq x \leq... show full transcript

Worked Solution & Example Answer:The table in Part (a)(ii) below shows some of the values of the function: $$h(x) = 0.001x^3 - 0.12x^2 + px + 5, \, x \in \mathbb{R}$$ in the domain $$0 \leq x \leq 75$$ - Leaving Cert Mathematics - Question 8(a) - 2021

Step 1

Use $$h(10) = 30$$ to show that $$p = 3.6$$

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Answer

To find the value of pp, we substitute x=10x = 10 into the function:

h(10)=0.001(10)30.12(10)2+p(10)+5h(10) = 0.001(10)^3 - 0.12(10)^2 + p(10) + 5

Calculating each term:

  1. 0.001(10)3=0.0011000=10.001(10)^3 = 0.001 \cdot 1000 = 1
  2. 0.12(10)2=0.12100=12-0.12(10)^2 = -0.12 \cdot 100 = -12
  3. The expression becomes:

h(10)=112+10p+5=30h(10) = 1 - 12 + 10p + 5 = 30

Combining the constants:

6+10p=30-6 + 10p = 30

Adding 6 to both sides gives:

10p=3610p = 36

Now, dividing by 10:

p=3.6p = 3.6

Step 2

Complete the table below and hence draw the graph of $$h(x)$$ in the domain $$0 \leq x \leq 75$$

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Answer

To complete the table, we will calculate the values of h(x)h(x) for the missing inputs:

  1. For x=20x = 20: h(20)=0.001(20)30.12(20)2+3.6(20)+5h(20) = 0.001(20)^3 - 0.12(20)^2 + 3.6(20) + 5 Compute: h(20)=0.001(8000)0.12(400)+72+5=848+72+5=37h(20) = 0.001(8000) - 0.12(400) + 72 + 5 = 8 - 48 + 72 + 5 = 37

  2. For x=30x = 30: h(30)=0.001(30)30.12(30)2+3.6(30)+5h(30) = 0.001(30)^3 - 0.12(30)^2 + 3.6(30) + 5 Compute: h(30)=0.001(27000)0.12(900)+108+5=27108+108+5=32h(30) = 0.001(27000) - 0.12(900) + 108 + 5 = 27 - 108 + 108 + 5 = 32

  3. For x=40x = 40: h(40)=0.001(64,000)0.12(1600)+144+5=64192+144+5=21h(40) = 0.001(64,000) - 0.12(1600) + 144 + 5 = 64 - 192 + 144 + 5 = 21

  4. For x=50x = 50: h(50)=0.001(125,000)0.12(2500)+180+5=125300+180+5=10h(50) = 0.001(125,000) - 0.12(2500) + 180 + 5 = 125 - 300 + 180 + 5 = 10

  5. For x=60x = 60: h(60)=0.001(216,000)0.12(3600)+216+5=216432+216+5=5h(60) = 0.001(216,000) - 0.12(3600) + 216 + 5 = 216 - 432 + 216 + 5 = 5

  6. For x=70x = 70: h(70)=0.001(343,000)0.12(4900)+252+5=343588+252+5=12h(70) = 0.001(343,000) - 0.12(4900) + 252 + 5 = 343 - 588 + 252 + 5 = 12

  7. For x=75x = 75: h(75)=0.001(421875)0.12(5625)+270+5=421.875675+270+5=21.875h(75) = 0.001(421875) - 0.12(5625) + 270 + 5 = 421.875 - 675 + 270 + 5 = 21.875

The completed table is:

x01020304050607075
h(x)30303732211051221.875

To draw the graph, plot all these points on the grid, ensuring the appropriate connections are made between points.

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