Question

if x=√3-√2thenx+1/x=?

Answer 1

If x+1/x=3, then what is the value of x³+1/x³=?

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Dev Kumar, Content Manager at Scholr

Answered Aug 25, 2018 · Author has 490answers and 253.5k answer views

It is given that

x+1x=3x+1x=3

Taking cubes on both sides,

(x+1x)3=33(x+1x)3=33

Since,

(a+b)3=a3+3a2b+3ab2+b3(a+b)3=a3+3a2b+3ab2+b3

Therefore,

x3+3x2x+3xx2+1x3=27x3+3x2x+3xx2+1x3=27

x3+3x+3x+1x3=27x3+3x+3x+1x3=27

x3+1x3+3(x+1x)=27x3+1x3+3(x+1x)=27

x3+1x3+3(3)=27x3+1x3+3(3)=27

x3+1x3+9=27x3+1x3+9=27

x3+1x3=27−9x3+1x3=27−9

x3+1x3=18

you can do it in this way