 Our students have topped the state in the TANCET and have secured admits in Anna University Chennai, SSN, and PSG # 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

#### 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 CourseTry it Free!

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