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  1. If x = p +
    1
    and y = p -
    1
    , then the value of x4 - 2x2y2 + y4 is :
    pp

    1. 24
    2. 4
    3. 16
    4. 8
Correct Option: C

x = p +
1
p

y = p -
1
p

∴ x + y = p +
1
+ p -
1
= 2p
pp

x - y = p +
1
- p +
1
=
2
ppp

∴ x4 - 2x2y2 + y4 = ( x2 - y2 )2 = { (x - y)(x + y) }2
x4 - 2x2y2 + y4 = 2p ×
2
2 = 42 = 16
p



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