## anonymous 5 years ago Amistre64, still around?

1. amistre64

... is that a fat joke?...

2. anonymous

lol. I'm so glad to have you to lighten up the fact that calculus stinks! i have a piecewise function to type in here. Let me try to do it without the equation thingy,ok?

3. amistre64

. . . . . . *splat*

4. anonymous

-2x-3, x<or = to 2 -2x+5, x>2 Need to find where this is undefined. How?

5. amistre64

-2x-3, x </ 2 -2x+5, x > 2

6. amistre64

the y value is defined for all cases; there is a gap between the lines at x=2 but it is still defined there

7. watchmath

Let me write it down in more beautiful typesett :D $$\begin{cases}-2x-3&,x\leq 2\\-2x+5&,x>2\end{cases}$$

8. amistre64

maybe its asking for the missing gap?

9. amistre64

(-7,1) perhaps; do we have options?

10. watchmath

Maybe asking where the function is discontinuous.

11. anonymous

Ok, here's what it is asking for: To find where y' is undefined, find the value of x where the derivative on one side is different than the derivative on the other side. Does that make sense to you?

12. anonymous

Amistre64, are you still here?

13. amistre64

yes, english is my native tongue

14. watchmath

When the function is discontinuous at a point, then the derivative is undefined there/ So y' is undefined at x=2.

15. amistre64

the derivative of both side = -2

16. amistre64

the derivatives are never different, so I assume the answer is defined for all x

17. amistre64

y ' = -2 at x=2

18. amistre64

y = -2x+5 at x=2 its defined there by the domain (-inf,2]

19. amistre64

it jumps yes; but it is defined

20. watchmath

That is not correct amistre64. Remember that diffferentiability implies continuity.

21. amistre64

im reading up on that now :) but does "undefined" pertain to jumps? id like to verify your answer :)

22. amistre64

the limit from the left and the limit from the right of piecewise function may be different; so the limit of the function does not exists at x=2

23. amistre64

the limit exists from the left; and from the right; but the two are not the same...

24. watchmath

you can try to use the definition of derivative to check it.

25. anonymous

Thanks again! I'm sure I'll be back!

26. amistre64

i had to first figure out what the question was.. you did good watchmath :)