Nov. 5, 2011 International SAT Math Lvl 2 Discussion

<p>what was your response for the problem with i?</p>

<p>@mgrigore21 The very last one?</p>

<p>in the problem where we had to choose among the methods I,II,and III for calculating the intersections with a calculator, I think that III is false. and here’s my reasoning why.</p>

<p>f(x) = x^2 and g(x) = 2x-2 doesn’t have any intersections together,
but if h(x) = f(x)-g(x) = x^2-2x+2 = (x-1)(x-1) = (x-1)^2</p>

<p>The method indicates that there is an intersection when x=1, but the value of f(1)=1 and the value of g(1)=0. so the method doesn’t work?</p>

<p>@mgrigore21 I think I chose b. it was -1+2a or something</p>

<p>Umm… (x-1)^2 = x^2 - 2x + 1. Not + 2.</p>

<p>either way. what rabbitfoot says is right…</p>

<p>what did people get for the expotential regression problem?</p>

<p>any other problems guys??</p>

<p>what’s the period of absolute value of tan(2x),</p>

<p>I just ignored the absolute value sign so it’s pi/2…</p>

<p>also guys the question to</p>

<p>f(x+3) = f(x) * f(3) thing?</p>

<p>e^x ?</p>

<p>@rabbitfoot I don’t think you are correct. Use your example again, f(x)=x^2 and g(x)=2x-2, h(x)=x^2-2x+2
For h(x)=0, delta of x^2-2x+2<0 and it has no solution which indicates that they have no intersection, which matches the graphical interpretation of the two functions.
h(x)=f(x)-g(x)=0 is simply equivalent to solving f(x)=g(x) which means the intersection of the two functions, it is the same as I.</p>

<p>for the regression i had 321 million ppl</p>

<p>I just drew a table to search for periodicity, as my intuition told me it’s very tricky to simply derive it out in such a limited time.</p>

<p>x |tan 2x|
pi/8 1
2pi/8 infinity
3pi/8 1
4pi/8 0
5pi/8 1
6pi/8 infinity
7pi/8 1
8pi/8 0

The function repeats itself for every ‘infinity’, i.e. tan pi/2, appears
Hence the period=6pi/8-2pi/8=pi/2</p>

<p>@warsovereign</p>

<p>that long list got me scared but then good thing it’s pi/2 lol</p>

<p>@superchicken777</p>

<p>umm is it in millions? </p>

<p>i thought it was weeks</p>

<p>the answer was 24, but I found it a really strange question for SAT II. I went home, and looked up how to graph exponential regressions, and at 10000, it’s 24 weeks. Also, for the f(x) and g(x) intercepts, it’s I and III because, if f(x) - g(x) = 0, that means that at point x, the y coordinate is the same.</p>

<p>also, the very last question with i was -1-2i, since the pattern repeats every 4th term. the 11th term is -1 - 2i, and it’s exactly 88 terms from 99. 88 is a multiple of 4, so the 99th term is -i - 2i</p>

<p>@VeryPractical
for “what’s the period of absolute value of tan(2x)”
My precalc teacher told me to set whatever is in the parenthesis to 0 and 2pi if it’s sine or cosine and then if it’s tangent to set it equal to 0 and pi. He never explained why but it always works for me. So I got pi/2 like warsovereign did (:</p>

<p>@jasminny</p>

<p>yea got it thanks</p>

<p>it’s pi/2 indeed lol</p>

<p>What was the answer for: If f(x+3) = f(x)*f(3) what is f?</p>

<p>did anybody try graphing [tan(2x)] at xmin=-4pi and xmax=4pi?</p>

<p>the period doesn’t look like pi/2</p>

<p>also, yeah i made a stupid calculation error. I and II are correct. i guess i already got 1 wrong. </p>

<p>by the way, for the linear digression problem did you guys choose 8,10,10,10,10,12?</p>