Question

Find value of x cube plus 1/x cube when x plus 1/x equals to 7

Answer 1

Answer:

x+1/x=7

Taking cube on both sides

(x+1/x)^3=(7)^3

Using formula:

(a+b)^3=a^3+3a^2b+3ab^2+b^3

we get

(x)^3+3(x)^2(1/x)+3(x)(1/x)^2+(1/x)^3=343

x^3+1/x^3+3(x)(1/x)(x+1/x)=343

x^3+1/x^3+3(7)=343

x^3+1/x^3+21=343

x^3+1/x^3=343-21

x^3+1/x^3=322

Step-by-step explanation:

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