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Answer:
108+76root2 is the answer
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Given:-
→x-1/x= 3+2√2
To find:-
→Value of x³-1/x³
Solution:-
We know that:-
=>(a-b)³=a³-b³-3ab(a-b)
We shall use the above identity to find the answer.
=>(x-1/x)³ = (x³-1/x³)-3×x×1/x(x-1/x)
=>(x-1/x)³ = (x³-1/x³)-3(x-1/x)
=>x³-1/x³ = (x-1/x)³+3(x-1/x)
=>x³-1/x³ = (3+2√2)³+3(3+2√2)
=>x³-1/x³ = 3+2√2[ (3+2√2)²+3 ]
=>x³-1/x³ = 3+2√2(9+8+3+12√2)
=>x³-1/x³ = (3+2√2)(20+12√2)
=>x³-1/x³ = 3(20+12√2)+2√2(20+12√2)
=>x³-1/x³ = 60+36√2+40√2+48
=>x³-1/x³ = 108+76√2
Thus,value of (x³-1/x³) is (108+76√2).
Some Extra Identities:-
•(a+b)³ = a³+b³+3ab(a+b)
•(a-b)³ = a³-b³-3ab(a-b)
•(a³+b³) = (a+b)(a²+b²-ab)
•(a³-b³) = (a-b)(a²+b²+ab)
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