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
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 $$0 \leq x \leq... show full transcript
Worked Solution & Example Answer:The table in Part (a)(ii) below shows some of the values of the function:
$$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$$
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Answer
To find the value of p, we substitute x=10 into the function:
h(10)=0.001(10)3−0.12(10)2+p(10)+5
Calculating each term:
0.001(10)3=0.001⋅1000=1
−0.12(10)2=−0.12⋅100=−12
The expression becomes:
h(10)=1−12+10p+5=30
Combining the constants:
−6+10p=30
Adding 6 to both sides gives:
10p=36
Now, dividing by 10:
p=3.6
Step 2
Complete the table below and hence draw the graph of $$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) for the missing inputs:
For x=20:
h(20)=0.001(20)3−0.12(20)2+3.6(20)+5
Compute:
h(20)=0.001(8000)−0.12(400)+72+5=8−48+72+5=37
For x=30:
h(30)=0.001(30)3−0.12(30)2+3.6(30)+5
Compute:
h(30)=0.001(27000)−0.12(900)+108+5=27−108+108+5=32
For x=40:
h(40)=0.001(64,000)−0.12(1600)+144+5=64−192+144+5=21
For x=50:
h(50)=0.001(125,000)−0.12(2500)+180+5=125−300+180+5=10
For x=60:
h(60)=0.001(216,000)−0.12(3600)+216+5=216−432+216+5=5
For x=70:
h(70)=0.001(343,000)−0.12(4900)+252+5=343−588+252+5=12
For x=75:
h(75)=0.001(421875)−0.12(5625)+270+5=421.875−675+270+5=21.875
The completed table is:
x
0
10
20
30
40
50
60
70
75
h(x)
30
30
37
32
21
10
5
12
21.875
To draw the graph, plot all these points on the grid, ensuring the appropriate connections are made between points.
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