Ascent TANCET Classes

XAT 2015 Quant & DI: Functions

This aptitude practice question appeared as a part of the quantitative reasoning and data interpretation section of the XAT 2015. Question 11 of a total of 33 questions that appeared in this section in XAT 2015. This one is a medium level difficulty question and tests the concept of equating f(0) of a function given two instances of the function.

Question

If f(x2 – 1) = x4 – 7x2 + k1 and f(x3 – 2) = x6 – 9x3 + k2 then the value of (k2 – k1) is

  1. 6
  2. 7
  3. 8
  4. 9
  5. None of the above

  Correct Answer      Choice C. The value of (k2 – k1) is 8


Explanatory Answer

Given Data

f(x2 – 1) = x4 – 7x2 + k1

f(x3 – 2) = x6 – 9x3 + k2

Approach and Solution

When x2 = 1, f(x2 – 1) = f(1 - 1) = f(0) =(1)2 - 7(1) + k1
f(0) = - 6 + k1 ..........(1)
Essentially, we have replaced all x2 with 1.

When x3 = 2,f(x3 – 2) = f(2 - 2) = f(0) =(2)2 - 9(2) + k2
f(0) = - 14 + k2 ..........(2)
Essentially, we have replaced all x3 with 2.

Equating f(0) in equations (1) and (2)
(-6 + k1) = (-14 + k2)
or k2 - k1 = 8

  The correct answer is Choice C.

Video Explanation

Online TANCET MBA Course
Try it Free!

Register in 2 easy steps and start learning in 5 minutes!

Already have an Account?

Login to continue

XAT TANCET Practice Questions - Listed Topic wise

Contact Us

Ascent Education
14B/1 Dr Thirumurthy Nagar I Street
Nungambakkam, Chennai 600 034
E mail: ascent@ascenteducation.com
Phone: +91 44 4500 8484
Mobile: +91 96000 48484