Numerical Ability

What is the value of x in x^(1/3) – x^(1/9) = 60

Question:-

question-1

Explanation:

To simplify the equation, let us consider-

equation-1

We should also change the second term in y form-

equation-2

By putting the value of x from equation (1) in (2)

equation-3

Therefore,

equation-4

Now, to solve this polynomial equation we find the factors of the constant value 60 and substitute y with each factor for checking whether it makes the equation equals 0. Whichever factor will make the equation equals 0 will be the value of y.

So the factors of 60 are = 5×4×3

By substituting 5 in place of y,

equation-5

Now we check the next factor 4

equation-6

Hence, y = 4

Note: We could also do above calculations mentally to save the time.

From the equation (1) we know that

equation-7

Hence, the correct choice is option (b)

 

You can read below concepts to solve this type of questions:

  1. How to Factor a Cubic Polynomial
  1. Fractional (Rational) Exponents

 

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