(x)^3+(1/×)^3=110 find x+1/x
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(x)^3 + (1/x)^3 = 110
= (x+ 1/x)^3 - 3 ( x + 1/x) = 110
Let x+ 1/x be a
=> a^3 - 3a = 110
=> a (a^2 - 3) = 110
Now comes the tricky part.
Let's try to divide 110 into two parts.
110 × 1
10 × 11
2 × 55
5 × 22
Test where the a^2 - 3 condition is applicable, i.e put the values and see if a perfect square will come.
(I'll skip the testing part)
a^2 - 3 = 22
a^2 = 25
a = 5
Thus, x+ 1/x = 5
Cheers!
= (x+ 1/x)^3 - 3 ( x + 1/x) = 110
Let x+ 1/x be a
=> a^3 - 3a = 110
=> a (a^2 - 3) = 110
Now comes the tricky part.
Let's try to divide 110 into two parts.
110 × 1
10 × 11
2 × 55
5 × 22
Test where the a^2 - 3 condition is applicable, i.e put the values and see if a perfect square will come.
(I'll skip the testing part)
a^2 - 3 = 22
a^2 = 25
a = 5
Thus, x+ 1/x = 5
Cheers!
abhi178:
Nice answer !!!
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