Question

if x+1/x=5 find x³+1/x³
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Answer 1

Step-by-step explanation:

use formula a^3+b^3

x^3+1/x^3 = (x+1/x)(x^2-x*1/x+1/x^2)

now x^2+1/x^2 = (x+1/x)^2 - 4x*1/x

= 5^2-4

25-4

=21

now again coming to our main formula

(x+1/x)(x^2-x*1/x+1/x^2)

5(x^2 + 1/x^2 -1)

5(21-1)

20*5

100 (answer)