Factors of x4 + 5x2 + 9 are :(a) (x2 + 2x + 3)(x2 + 3x + 3) (b) (x2

1.	Factors of x4 + 5x2 + 9 are :(a) (x2 + 2x + 3)(x2 + 3x + 3) (b) (x2 - 2x + 3)(x2 - 3x - 3) (c) (x2 - 2x - 3)(x2 + 3x + 3) (d) (x2 - 2x + 3)(x2 + 3x + 3)
Answer» (d) (x² - 2x + 3)(x² + 3x + 3) x⁴ + 5x² + 9 = x⁴ + 6x² + 9 - x² (Note the step) = (x² + 3)² - x² Now, factorise using x² - y² = (x + y)(x - y)

Factors of x4 + 5x2 + 9 are :(a) (x2 + 2x + 3)(x2 + 3x + 3) (b) (x2 - 2x + 3)(x2 - 3x - 3) (c) (x2 - 2x - 3)(x2 + 3x + 3) (d) (x2 - 2x + 3)(x2 + 3x + 3)

Answer»

(d) (x² - 2x + 3)(x² + 3x + 3)

x⁴ + 5x² + 9

= x⁴ + 6x² + 9 - x² (Note the step)

= (x² + 3)² - x²

Now, factorise using x² - y² = (x + y)(x - y)