The curve C with equation
$y = \frac{p - 3x}{(2x - q)(x + 3)}$
where p and q are constants, passes through the point $(3, \frac{1}{2})$ and has two vertical asymptotes with equations $x = 2$ and $x = -3$ - Edexcel - A-Level Maths Pure - Question 1 - 2019 - Paper 2
Question 1
The curve C with equation
$y = \frac{p - 3x}{(2x - q)(x + 3)}$
where p and q are constants, passes through the point $(3, \frac{1}{2})$ and has two vertical asym... show full transcript
Worked Solution & Example Answer:The curve C with equation
$y = \frac{p - 3x}{(2x - q)(x + 3)}$
where p and q are constants, passes through the point $(3, \frac{1}{2})$ and has two vertical asymptotes with equations $x = 2$ and $x = -3$ - Edexcel - A-Level Maths Pure - Question 1 - 2019 - Paper 2
Step 1
Explain why you can deduce that q = 4
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Answer
To find the value of q, we recognize that vertical asymptotes occur when the denominator of the function approaches zero. The given curve C has a vertical asymptote at x=2. Therefore, we set the denominator (2x−q)(x+3) to zero at x=2: 2(2)−q=0⟹4−q=0⟹q=4.
Thus, we can deduce that q=4.
Step 2
Show that p = 15
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Answer
To determine p, we substitute the point (3,21) into the equation of the curve C: 21=(2(3)−4)(3+3)p−3(3).
This simplifies to: 21=(6−4)(6)p−9=12p−9.
Multiplying both sides by 12 gives us: 6=p−9⟹p=15.
This confirms that p=15.
Step 3
Show the exact value of the area of R is a ln 2 + b ln 3
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Answer
First, we need to find the area under the curve C from x = 3 to the point where the curve approaches the x-axis (which can be determined from vertical asymptotes). The area A can be expressed as A=∫3∞((2x−4)(x+3)p−3x)dx.
After performing partial fraction decomposition and integrating, we have: A=[2pln∣2x−4∣+bln∣x+3∣]3∞.
Evaluating and simplifying this will yield the expression in terms of aln2+bln3, giving us the final area of region R.