x4 + 6x2 - 7 এর উৎপাদক গুলো হলো-
A (x2 + 7)(x + 2)(x - 2)
B (x2 - 7)(x + 1)(x - 1)
C (x2 + 7)(x + 1)(x - 1)
D (x2 - 7)(x - 1)(x - 1)
Solution
Correct Answer: Option C
x4 + 6x2 - 7
= (x2)2 + 2.x2.3 + 32 - 9 - 7
= (x2 + 3)2 - 42
= (x2 + 3 + 4)(x2 + 3 - 4)
= (x2 + 7)(x2 - 1)
= (x2 + 7) (x2 - 12)
= (x2 + 7)(x + 1)(x - 1)