expansion expansion expansion 1 and 3
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Step-by-step explanation:
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Answered by
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1) 2
2) 322
Step-by-step explanation:
1) If x + 1/x = 2, find x³ + 1/x³
x + 1/x = 2
Cubing on both sides
( x + 1/x )³ = 2³
Using algebraic identity (a + b)³ = a³ + b³ + 3ab(a + b)
x³ + 1/x³ + 3(x)(1/x)( x + 1/x ) = 8
x³ + 1/x³ + 3(2) = 8
x³ + 1/x³ + 6 = 8
x³ + 1/x³ = 8 - 6 = 2
Therefore the value of x³ + 1/x³ is 2.
2) If 3x + 1/3x = 7, find 27x³ + 1/27x³.
3x + 1/3x = 7
Cubing on both sides
( 3x + 1/3x )³ = 7³
Using algebraic identity (a + b)³ = a³ + b³ + 3ab(a + b)
( 3x )³ + ( 1 /3x )³ + ( 3x )( 1/3x )( 3x + 1/3x ) = 343
27x³ + 1/27x³ + 21 = 343
27x³ + 1/27x³ = 343 - 21 = 322
Therefore the value of 3x + 1/3x is 322.
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