Help to Integral Calculus Solutions & Examples

Recent questions in Integral Calculus
Integral CalculusAnswered question
Jean Farrell Jean Farrell 2022-09-17

Find the interval in which f(x) increases and decreases.
Let f ( x ) = 2 x 3 9 x 2 + 12 x + 6 so f ( x ) = 6 x 2 18 x + 12 = 6 ( x 1 ) ( x 2 ).
I need the intervals in which f(x) strictly increases, f ( x ) > 0 when x < 1 and x > 2 and thus f(x) strictly increases in these intervals and f ( x ) < 0 when 1 < x < 2 so f(x) strictly decreases in this interval.
My Question:
What about at points x = 1 , 2.
If f ( x ) = 0 at points (not intervals) then f(x) can still be considered strictly monotone. And it also seems reasonable (I'll add the reason below) to include the points 1,2 in the intervals of increase (IOI, for short) and decreases (IOD).
Eg: Take x = 1. Let's say I include this point in both IOI and IOD. So IOI is now, x ( , 1 ] and you can see that it doesn't contradict the definition of "strictly increasing function in interval" either. Take any p , q ( , 1 ] , p > q f ( p ) > f ( q ) similarly my IOD, now would be x [ 1 , 2 ] (notice I included 2) and it still follows the definition.
As I understand that, definition of monotonicity functions at a point, would now get in the way.
I can't include x = 1 because there exists no h > 0 such that taking p , q ( 1 h , 1 + h ) f ( p ) > f ( q ) similarly, I can't add x = 1 in interval of decrease either.
If I'd have to pick, my intuition would lead me to pick the second one, but I can't see why I should reject the first one either since it actually follows the definition of strictly increasing function in interval.

If you’re looking for integral calculus problems with answers, you came to the right place. We offer help with various integral calculus practice problems with explanations. Take a look at the answers. These will contain not only calculations and algebraic equations because integral calculus includes integral word problems that are often provided as a way to help students learn. It’s also a reason why most people struggle with calculus integral problems and approach them as something more complex than it really is. See various answers to integral calculus problems and remember to compare your instructions with the solutions provided below.