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 2 - 2019 - Paper 1
Question 2
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 2 - 2019 - Paper 1
Step 1
Explain why you can deduce $q = 4$
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Answer
Given the equation of the curve, the vertical asymptotes occur when the denominator equals zero.
For the asymptote at x=2, we have: 2(2)−q=0.
This leads to: 4−q=0,
therefore, q=4.
This indicates that for any value of x approaching 2, the function approaches infinity, confirming x=2 as a vertical asymptote.
Step 2
Show that $p = 15$
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Answer
To find p, substitute the point (3,21) into the curve's equation.
Setting y=21 when x=3, we have: 21=(2(3)−4)(3+3)p−3(3)
This simplifies to: 21=(6−4)(6)p−9 21=2⋅6p−9
Multiplying both sides by 12 results in: 6=p−9
Thus, solving for p gives:
p = 15.
Step 3
Show that the exact value of the area of $R$ is $a \ln 2 + b \ln 3$
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Answer
To find the area of region R, set up the integral bounded by the curve and the line x=3.
This is expressed as:
Area=∫03ydx=∫03(2x−4)(x+3)p−3xdx
Substituting p=15 gives:
∫03(2x−4)(x+3)15−3xdx.
Use partial fractions to decompose the integrand which leads to finding constants A and B, so:
(2x−4)(x+3)15−3x=2x−4A+x+3B.
By solving for A and B, proceed to evaluate the integral from 0 to 3, leading to the exact area in the form of aln2+bln3.