OpenStudy (iwanttogotostanford):

AM I RIGHT HERE? CALC.

1 year ago
OpenStudy (iwanttogotostanford):

1 year ago
OpenStudy (iwanttogotostanford):

?

1 year ago
OpenStudy (triciaal):

please repost the graph not very clear

1 year ago
OpenStudy (iwanttogotostanford):

@triciaal sorry, here is the new one

1 year ago
OpenStudy (iwanttogotostanford):

@mathmate @triciaal @Loser66

1 year ago
OpenStudy (triciaal):

it posted correctly can see everything now

1 year ago
OpenStudy (triciaal):

@mathmale

1 year ago
OpenStudy (triciaal):

not the solution but B is a parabola the derivative would be a straight line

1 year ago
OpenStudy (triciaal):

@sshayer do you think A or C?

1 year ago
OpenStudy (triciaal):

@mathmale

1 year ago
OpenStudy (triciaal):

sorry should be @mathmate thanks @SolomonZelman

1 year ago
OpenStudy (solomonzelman):

The derivative of the curve $$f(x)$$, as we know by its limit definition, is the instantaneous slope of $$f(x)$$ at any point x, and it is given by $$f'(x)$$. So, if you see at $$x=\alpha$$ that $$f_1(x)$$ is increasing and $$f_2(\alpha)<0$$, then $$f_2(x)\ne f_1'(x)$$

1 year ago
OpenStudy (solomonzelman):

Alternatively, (the other way around) if at $$x=\alpha$$, you have a decreasing $$f_1(x)$$, and $$f_1(\alpha)>0$$, then again $$f_1'(x)\ne f_2(x)$$.

1 year ago
OpenStudy (solomonzelman):

I am just going by definition that if a function is decreasing at a point, the slope (or the derivative) at this point should be negative. Or, if a function is increasing, the slope (or the derivative) at this point should be positive.

1 year ago
OpenStudy (solomonzelman):

Look at x=0 carefully.

1 year ago
OpenStudy (solomonzelman):

The slope of B is positive, but A<0. So A$$\ne$$B'.

1 year ago
OpenStudy (solomonzelman):

Are you following with me? (If you lose me let me know.)

1 year ago
OpenStudy (solomonzelman):

Looks like actually the function B can model the slope of function A.

1 year ago
OpenStudy (solomonzelman):

(1) Before the first horizontal tangent, B is A is increasing but concave down. how can we tell this from the graph of A? Look at the tangent lines (before the turn), you will see their slope is positive, but this slope decreases. And so we have the correspondence from B. B is positive and decreases. The horizontal tangent points on curve A, correspond to values of B=0. etc...

1 year ago
OpenStudy (solomonzelman):

Just examine curve A (at points x=δ), and see if B can (or cannot) fit as a slope at x=δ.

1 year ago
OpenStudy (solomonzelman):

(for any x=δ you deem to examine to reach conclusion you see sufficient)

1 year ago
OpenStudy (solomonzelman):

I never prohibited questions:)

1 year ago
OpenStudy (iwanttogotostanford):

@SolomonZelman thank you! i did all that and still ended up with A... is that correct??

1 year ago
OpenStudy (solomonzelman):

no

1 year ago
OpenStudy (iwanttogotostanford):