CAT Practice : Functions

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The concept of equating f(0) of a function given two instances of the function.

Functions - Value of p - q

    Q.9: If f(x – 3) = 2x3 + p – qx and f(x2 – 4) = x2 – 8q + 6p, then what is the value of p – q?
    1. 5
    2. 10
    3. 6
    4. Cannot determine

 

  • Correct Answer
    Choice B. 10

Detailed Solution

f(x – 3) = 2x3 + p – qx
Let x = 3, then f(0) = 54 + p – 3q ---- (1)

f(x2 – 4) = x2 – 8q + 6p
Let x2 = 4, then f(0) = 4 – 8q + 6p --- (2)

From (1) and (2)
54 + p – 3q = 4 – 8q + 6p
50 = 5p – 5q
p - q = 10

Answer choice (B).


Correct Answer: 10



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