Question

Hi, how to do question 10:)?

Answer 1

Step-by-step explanation:

For the cubic function to be an increasing function, dy/dx > 0 for all real values of x.

dy/dx

= d/dx [4x³ + 4px² + 16x - 9]

= 12x² + 8px + 16.

We have 12x² + 8px + 16 > 0.

=> 3x² + 2px + 4 > 0,

where a = 3, b = 2p and c = 4.

For the quadratic function to have a range that is always positive, the discriminant must be less than 0.

(in order to have no real roots)

We have b² - 4ac < 0.

=> (2p)² - 4(3)(4) < 0

=> 4p² - 48 < 0

=> p² - 12 < 0

=> p² < 12

=> -√12 < p < √12

=> -2√3 < p < 2√3.

That was a very long process but hopefully you understand all of it!