2012 AP Calculus AB Test Discussion

<p>What is the percentage u need to get to ensure 5</p>

<p>Mc: The vertical slope was root2 and root2</p>

<p>@mathisfun</p>

<p>i think it was like 2x+3/sqrt(x^2+5) or something like that because the bottom is always positive and then when you go to +infinity you get +/+ so it’s 2 and then negative infinity it’s -/+ so it’s -2…</p>

<p>and totally blanking out on the frq… i just remember there was this bird problem and writing YOLO all over it LOLLL</p>

<p>EDIT: bird one was like dB/dt=1/5(100-B)
a) is dB increasing faster when B=40 or 70 and it was 40 because
1/5(100-40)=12g/day and then B’(70)=1/5(100-70)=6g/day and 12>6 so at 40 grams the rate is faster</p>

<p>b)dB/dt=20-B/5 dB^2/dt^2=(-1/5)B’ = -1/25(100-B)</p>

<p>B’’ is concave down for (0,100) and the graph showed that it was concave up for the first bit after 0 so therefore the graph couldn’t be right</p>

<p>c)B(0)=20 find the specific equation</p>

<p>dB/dt=(1/5)(100-B)
(1/(100-B))dB=dt/5
-ln(100-B)=t/5+c
e^(-ln(100-b))=Ce^(t/5)
B-100=Ce^(t/5)
B=Ce^(t/5)+100
20=C(1)+100
C=-80
B(t)=-80e^(t/5)+100</p>

<p>that was 5 or 6 i thinkkk</p>

<p>EDIT 2:</p>

<p>A)find R under y=lnx and y=5-x
5-x=lnx
x=3.6934414=a</p>

<p>integral from (1,a)(lnx)dx+ integral from (a,5)(5-x)dx =2.986ish</p>

<p>C) find the volume with squares parallel to the x-axis</p>

<p>integral (1,a)(lnx)^2dx+(a,5)(5-x)^2dx… did we have to calculate?</p>

<p>D) find the x=k that will split R into 2 equal parts</p>

<p>.5*(integral (1,a)(lnx)dx+integral (a,5)(5-x)dx)=integral (1,k)(lnx)dx</p>

<p>@Bro, I think I got that! However, was there one where the sq root was on the top with the squared in it?</p>

<p>I can’t remember what exactly i put, all i know is it had a sq root and a squared in it :P</p>

<p>I got 15 for the one you guys got 18. Wasn’t the integral from 1 to 6, not 0 to 6? I may be wrong.</p>

<p>No the answer to that has the denominator with the root AND sqaure, thus putting an absolute sign around it. And the degree of the top n bottom has to be the same</p>

<p>If u draw a straight line, get a triangle and a rectangle, the area is not maximized. U need to draw a full rectangle, whose area is 18</p>

<p>I think I did pretty good. Non Calculator MC was pretty easy, I got OWNED on calculator MC though, and the FRQs were relatively easy too. Hoping I got a 4 or 5. LOL at FRQ 4…Was that unexpectedly simple or what?</p>

<p>I put 18 first… then i thought it was too easy and put 15… sooo ****ed!</p>

<p>Thank GOODNESS I put 18!!! I put 15 at first, then changed it because the interval was less than or equal to or whatever.</p>

<p>anyone remember an answer with the integral of 2/t? i put the absolute value of it.</p>

<p>What did u guys pick for choosing a graph based on dydx at (1,1)? I put d ( differentiated dydx and found if it was neg or pos ) ( the first dydx at 1,1 was 0)</p>

<p>I got 18 and yes I got the integral of the absolute value of 2/t</p>

<p>Just change in temp. It goes into m(40) - m(20)</p>

<p>How do you guys remember all of your answers? I already forgot em :P. </p>

<p>I hope I got a 5. It was so much easier than expected, but there are a few MC Calculator and FRQs that I’m not too confident on.</p>

<p>I assume the scale won’t be so forgiving this year though, right?</p>

<p>Wait I forgot what FRQ # 4 was asking…can someone help me out?</p>

<p>like why is everyone saying 18 :x</p>

<p>For one of the non-calc free response, it talk about whether the velocity was increasing or decreasing.Which did you guys say?Not sure if that double negative rules for v and a applied there.</p>

<p>The question asked for the speed and since velocity and acceleration were both negative the speed was increasing.</p>

<p>I dont think there was anything asking for speed</p>

<p>@Meburi</p>

<p>dY/dx=(x-1)Y^2</p>

<p>Y is always positive and x is positive (1,infinity) and negative (-infinity,1)
so therefore it was the graph that was decreasing and then increasing after x=1 like a U</p>