AM I RIGHT HERE? CALC.

Question

iwanttogotostanford · Answer

please lmk anyone!

iwanttogotostanford · Answer

?

triciaal · Answer

please repost the graph  not very clear

iwanttogotostanford · Answer

@triciaal sorry, here is the new one

iwanttogotostanford · Answer

@mathmate @triciaal @Loser66

triciaal · Answer

it posted correctly  can see everything now

triciaal · Answer

@mathmale

triciaal · Answer

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

triciaal · Answer

@sshayer do you think A or C?

triciaal · Answer

@mathmale

triciaal · Answer

sorry should be @mathmate thanks @SolomonZelman

solomonzelman · Answer

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 $f_2(x)\ne f_1'(x)$

solomonzelman · Answer

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

solomonzelman · Answer

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.

solomonzelman · Answer

Look at x=0 carefully.

solomonzelman · Answer

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

solomonzelman · Answer

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

solomonzelman · Answer

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

solomonzelman · Answer

(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...

solomonzelman · Answer

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

solomonzelman · Answer

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

solomonzelman · Answer

I never prohibited questions:)

iwanttogotostanford · Answer

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

solomonzelman · Answer

no

iwanttogotostanford · Answer

help someone please