The curve with equation
$y = x^2 - 32 ext{√}(x) + 20$,
$x > 0$
has a stationary point $P$ - Edexcel - A-Level Maths Pure - Question 4 - 2013 - Paper 4
Question 4
The curve with equation
$y = x^2 - 32 ext{√}(x) + 20$,
$x > 0$
has a stationary point $P$.
Use calculus
(a) to find the coordinates of $P$,
(b) to ... show full transcript
Worked Solution & Example Answer:The curve with equation
$y = x^2 - 32 ext{√}(x) + 20$,
$x > 0$
has a stationary point $P$ - Edexcel - A-Level Maths Pure - Question 4 - 2013 - Paper 4
Step 1
(a) to find the coordinates of P
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Answer
To find the coordinates of the stationary point P, we first need to calculate the first derivative of the equation.
Find the first derivative: dxdy=2x−32⋅2x1=2x−x16
Set the first derivative to zero: 2x−x16=0
Solve for x:
Rearranging gives us: 2x=x16
Squaring both sides leads to: 4x2=16
Thus: x2=4→x=2
Substitute x back to find y: y=22−32⋅2+20
Calculating gives: y=4−32⋅2+20=24−32⋅2
So, the coordinates of the stationary point P are (2,24−32⋅2).
Step 2
(b) to determine the nature of the stationary point P
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Answer
To determine the nature of the stationary point P, we will analyze the second derivative.
Find the second derivative: dx2d2y=2+2x3/216=2+x3/28
Evaluate the second derivative at x=2: dx2d2yx=2=2+(2)3/28=2+228=2+22
Since both terms are positive, we find that dx2d2y>0
This indicates that the stationary point P is a minimum.