Question
Question: Let f(x) = x<sup>2</sup> + bx + c where b, c Ī R. If f(x) is a factor of both x<sup>4</sup> + 6x<sup...
Let f(x) = x2 + bx + c where b, c Ī R. If f(x) is a factor of both x4 + 6x2+ 25 and 3x4 + 4x2 +28x +5 then the least value of f(x) is
A
2
B
3
C
5/2
D
4
Answer
4
Explanation
Solution
f(x) will also be factor of
3(x4 + 6x2 + 25) – (3x4 + 4x2 + 28x + 5)
= 14 (x2 – 2x + 5)
It means x2 – 2x + 5 & x2 + bx + c have both roots common
Hence least value of
f(x) = (x – 1)2 + 4 ³ 4