x + 1/x = 3 , find x³ + 1/x³
safura:
answer is 27-3(a2b-ab2)
the answer given is 18
Answers
Answered by
4
Let x be a
let 1/x be b
Therfore a*b=1
a+b=3
(a+b)^3=a^3+b^3+3ab(a+b)
a^3+b^3=(a+b)^3-3ab(a+b)
a^3+b^3=3^3-3*3{substituting the values}
a^3+b^3=27-9=18
now,
a^3=x^3
b^3=1/x^3
therefore,
x³ + 1/x³=18
Answered by
1
(X+1/x)^3-3x*1/x(x+1/x)=(3)^3-3*3=18
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