Q509
If (a + 4)3 = a3 + 12a2 + ka + 64, then what is the value of k?
A.
45
B.
46
C.
47
D.
48
AnswerAnswer: Option D
Solution
Answer: Option D
Solution:
(a + b)3 = a3 + 3a2b + 3ab2 + b3 . . . . . . . . (i)(a + 4)3 = a3 + 12a2 + ka + 64
= (a)3 + 3.a2.4 + k.a + (4)3 . . . . . . . . (ii)
Comparing equation (i) and (ii) we get,
b = 4 and k = 3k2
∴ k = 3 × 42 = 48