CAT 2006QA Question 15

Solving Quadratic EquationsEasy

What values of x satisfy x23+x13-20?

Answer & solution

Correct answer: –8 ≤ x ≤ 1

  • –8 ≤ x ≤ 1

  • B

    –1 ≤ x ≤ 8

  • C

    1 < x < 8

  • D

    1 ≤ x ≤ 8

  • E

    –8 ≤ x ≤ 8

Solution

x23+x13-20   ...(1)

Put y = x1/3

Then equation (1) becomes y2 + y – 2 ≤ 0

(y + 2)(y – 1) ≤ 0

–2 ≤ y ≤ 1

-2x131

–8 ≤ x ≤ 1

Hence, option (a).

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CAT 2006 QA Q15: What values of x satisfy x 2 3 + x 1 3 - 2 &le; 0 ? — Solution | TheCATExam