Question

3
5
If x2 +
1
= 27, find the value of 3x3 + 5x –
x2
23​

Answer 1

Answer:

Which sign before 23?

Step-by-step explanation:

Your question is incomplete.

Answer 2

Given :    x² + 1/x² = 27  

To find: 3x³  + 5x  - 3/x³  - 5/x

Solution:

x² + 1/x² = 27  

=> (x - 1/x)² + 2x(1/x) = 27

=>  (x - 1/x)²  = 25

=> (x - 1/x)  = ± 5

3x³  + 5x  - 3/x³  - 5/x

= 3(x³ - 1/x³)  + 5(x - 1/x)

= 3(x - 1/x)(x² + 1/x²  + x(1/x)  +  5(x - 1/x)

= 3(x - 1/x)(27 + 1) +  5(x - 1/x)

= 84 (x - 1/x) + 5(x - 1/x)

= 89(x - 1/x)

using (x - 1/x)  = ± 5

=  ± 445

3x³  + 5x  - 3/x³  - 5/x = ± 445    if   x² + 1/x² = 27  

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