Using (a–b)3 = a3 –b3 –3ab(a–b) tick the correct of these when x = p1/...
Solution:
Given: x = p1/3 – p–1/3
We need to find the correct option out of (a), (b), (c), and (d) using (a–b)3 = a3 –b3 –3ab(a–b).
Expansion of (a–b)3
(a–b)3 = a3 –b3 –3ab(a–b)
On putting a = p1/3 and b = p–1/3, we get
(p1/3 – p–1/3)3 = (p1/3)3 – (p–1/3)3 – 3(p1/3)(p–1/3)(p1/3 – p–1/3)
Simplifying the above expression, we get
p + 3p1/3 p–1/3(x) = 2p1/3 + 2p–1/3
Finding the value of x3 – 3x
Multiplying the above equation by p1/3, we get
p4/3 + 3p(x) – p2/3(x) = 2p + 2p2/3
Multiplying the above equation by p–2/3, we get
p1/3 + 3(x) – (x)(p–1/3) = 2p–1/3 + 2
Adding (x)(p–1/3) to both sides, we get
p1/3 + 3(x) = (x)(p1/3 + p–1/3) + 2p–1/3 + 2
Substituting the value of x = p1/3 – p–1/3, we get
p1/3 + 3(p1/3 – p–1/3) = (p1/3 – p–1/3)(p1/3 + p–1/3) + 2p–1/3 + 2
Simplifying the above expression, we get
3p1/3 – 3p–1/3 = p + 2p–1/3 + 2
Multiplying both sides by p1/3, we get
3p – 3 = p4/3 + 2p2/3 + 2p1/3
On simplifying the above expression, we get
p4/3 – 3p1/3 – 2p–1/3 – 3 = 0
Multiplying both sides by p1/3, we get
p5/3 – 3p2/3 – 2p1/3 – 3p1/3 = 0
p5/3 – 5p2/3 – 3p1/3 = 0
Multiplying both sides by p1/3, we get
p2 + 5p – 3 = 0
Solving the above quadratic equation, we get
p = (–5 ± √37)/2
Comparing the given options
(a) x3 3x = p 1/p
On substituting the value of x in the above
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