<p>Well, n^2 + 4n = n(n+4), 1<em>5 = 5, 3</em>7 = 1, 5<em>9 = 5, 7</em>1 = 7, 9*3 = 7. Still a bit slower than RandomHSer’s solution, but not too slow.</p>
<p>To be honest, I too probably would have just plugged in odd numbers if this were on the real SAT.</p>
<p><a href=“Dropbox - Error - Simplify your life”>Dropbox - Error - Simplify your life;
<p>PLEASE HELP</p>
<p>The sides of the trapezoids between the 80 degree angles form a regular n-gon, where n is the number of trapezoids that we’re solving for. Each interior angle is 80+80=160 degrees. But we know that in an n-gon, the sum of the interior angles is 180(n-2) (you can prove this by picking a point in the interior and drawing lines to each vertices, creating a bunch of triangles). So in a regular n-gon, each interior angle is 180(n-2)/n. So 180(n-2)/n=160, (n-2)/n=16/18. n=18. </p>
<p>@RandomHser YOU’RE AWESOME THANK YOU!</p>
<p>Uhm… how about this one?</p>
<p><a href=“Dropbox - Error - Simplify your life”>Dropbox - Error - Simplify your life; </p>
<p>Haha, thanks!</p>
<p>The vertex of y=-2(x-1)^2+2 is (1,2). The line going through (1,2) and (-1,-6) has slope (2-(-6))/(1-(-1))=4. So line l has slope 4 and thus so does line k. If a line has slope 4, then increasing the x-value of a point on the line by 1 and y-value by 4 will give another point on the line. (A)</p>
<p>oh and btw I sorta didn’t get your explanation for DrSteve’s question! </p>
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<p>Is it a known rule that “If the units digit of a square is 1, then the original number’s units digit is either 1 or 9”. are there other such rules I should study from somewhere o.o LOL </p>
<p>@2200andbeyondXD do you know what the answer is? I’m thinking it’s A</p>
<p>Nah, it’s not something worth memorizing. If you don’t see a clever way to do a problem like that you can always try plugging in numbers like the next two people did (which is a perfectly good way to solve it!).</p>
<p>But here’s how you might be able to quickly figure it out. If n is a whole number from 0 to 9, then (10-n)^2 has the same last digit of n^2. So once you notice that 1 works, 9 also works. This also knocks the numbers we need to check to odds between 1 and 5. But if you’re doing this much work already, it would have been more efficient to just plug in numbers. I just happened to know that only 1 and 9 worked off of the top of my head.</p>
<p>I might make an SAT math/math subject test guide at some point…</p>
<p>@Jellybae for which one?</p>
<p>@2200andbeyondXD 20</p>
<p><a href=“Dropbox - Error - Simplify your life”>https://www.dropbox.com/s/ld68ui48u5u9nr0/math.png?m=</a> this?</p>
<p>@Jellybae yes you’re right</p>
<p>Plug in x=1. a(1+1)^2-1=0. 4a=1, a=1/4.</p>
<p>A determines the how wide it is in general right?! @RandomHser</p>
<p>“a” I mean</p>
<p>Yes, larger magnitude a means narrower. The sign of a determines whether the parabola opens or down.</p>
<p>How hard can a parabola question come? I suck :(</p>
<p>Plugging in either of the two given points is the way to go with this problem. For example, if you plug in (1,0) you get </p>
<p>0 = a(1+1)^2 - 1 = a2^2 - 1= 4a - 1. So 4a = 1, and a = 1/4, choice (A).</p>
<p>Any problem with a parabola is for advanced students only. You can break a 700 without worrying about parabolas. If you are going for an 800, then you might want to know how to find the vertex of a parabola, be familiar with the standard form of a quadratic function, and know how the basic transformations work.</p>
<p>@DrSteve I actually got an 800 in the SAT before (no . matter how hard that is to believe:P)
I haven’t done math for over a year 
I am aiming for that too this test so please give me all the advanced tips u have!!!</p>
<p>Thank you! </p>