## IB Maths HL Monotonicity

Discussions for the Core part of the syllabus. Algebra, Functions and equations, Circular functions and trigonometry, Vectors, Statistics and probability, Calculus. IB Maths HL Revision Notes

### IB Maths HL Monotonicity

IB Mathematics HL– Differentiation, Monotonicity, Increasing Decreasing Function

How can we find the intervals where $f(x)$ is decreasing or increasing?

$f(x)=x^3+3x^2+5$

Thanks
Max

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Joined: Mon Jan 28, 2013 8:06 pm

### Re: IB Maths HL Monotonicity

IB Mathematics HL – Derivatives, , Monotonicity, Increasing Decreasing Function

Firstly we have to find the first derivative function

$f’(x)=3x^2+6x=3x(x+2)$

which is positive in the intervals

$(- \infty , -2)\cup (0, +\infty)$

and is negative in the interval $(-2,0)$

Therefore the function is increasing for

$x \in (- \infty , -2)\cup (0, +\infty)$

and is increasing for $x \in (-2,0)$

Hope these help!!
miranda

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Joined: Mon Jan 28, 2013 8:03 pm

### Re: IB Math HL Monotonicity

Thank you miranda!!
Max

Posts: 0
Joined: Mon Jan 28, 2013 8:06 pm