<p>I need a thorough explanation for the second one, please.</p>
<p>1.</p>
<p>it is negative because the slope is (y2-y1)/(x2-x1)
let r=4=y1 and s=5=x2
than, (0-4)/(5-0) is -4/5, which equals -r/s
you can tell if the slope is negative if it falls down to the right side, if it rises to the right side it is alway positive</p>
<p>btw i don’t know the second one :D</p>
<ol>
<li>E</li>
</ol>
<p>There are two strategies for 2.</p>
<p>The first, more obvious is to factor each equation to find which one doesn’t have x-1 as a factor</p>
<p>The second is much faster, but a little harder to notice.
If (x-k) is a factor of f(x), then f(k)=0. So, simply substitute 1 for x (make sure you realize it’s the opposite of the number given, if it had said x+1, you would substitute -1)
All of them will equal 0 except e.</p>
<p>BTW this is a late ALG 1, early ALG 2 concept, if you need a more thorough explanation, I can explain it more in detail.</p>
<p>Oh, I see. Subtracting the coordinates gives you negative, duh.</p>
<p>“btw i don’t know the second one”</p>
<p>Let’s hope someone else does. :p</p>
<p>@witty</p>
<p>You’ve lost me there with the function. More details would be good.</p>
<p>And here is a simple one I forgot how to do: [Improve</a> Your SAT Scores with the SAT Skills Insight](<a href=“http://sat.collegeboard.com/practice/sat-skills-insight/math/band/500/skill/9#skill3Example]Improve”>http://sat.collegeboard.com/practice/sat-skills-insight/math/band/500/skill/9#skill3Example)</p>
<p>Also, which angle rules are needed to solve this?</p>
<p>Have you had Alg. 2, I can explain the concept, but it would help if I knew how much math experience you have</p>
<p>For the angle one, remember that a triangle must have 180 total degrees.</p>
<p>The large triangle is isoceles, so you know that both base angles are equal.
180-40(the given angle)=140
since both angles are equal, divide by 2
140/2=70</p>
<p>Now you know both base angles are 70. Now work with the angle bisectors. The base angles of the smaller triangle must both = 35 because 70/2=35.</p>
<p>Now subtract those two angles from 180 to get 110.
180-35-35=110 answer a</p>
<p>@witty Not much, but explain it in as many ways as you could if you have time. :P</p>
<p>Ok, quadratic equations (in this case parabolas) are are equations where variables (x) are raised to the power of 2.</p>
<p>In high school algebra, you will probably work mainly with parabolas, which are shaped like u’s</p>
<p>When you have a quadratic function, it means y=ax^2+bx+c
where a, b, and c are coefficients, which will be given.
(In answer choice A, a=1, b=-3, and c=2)</p>
<p>When dealing with parabolas the main characteristics looked at are the vertex (bottom of the u if a is positive, top of the upsidedown u if a is negative)</p>
<p>Note: I’m just splitting it so I can know how much you need to know</p>
<p>A google image search will show you what parabolas look like.</p>
<p>Due to the shape of a parabola, their graphs have the potential to pass through the x-axis 0 times or 2 times.
When it passes through 0 times you deal with complex numbers (numbers involving i - I don’t think they appear on the SAT)
When it passes through twice, you can calculate its intercepts</p>
<p>Finding the intercepts requires a process called factoring, which writes the equation as a product of two binomials, instead of the sum of three terms. </p>
<p>ex. (2x+1)(x+1)=2x^2 + 3x + 1</p>
<p>Yes, I see. Thank you. I could also just quickly do the factoring on a ti-89 and compare.</p>
<p>And I got up to the 70 degree angle step, but wasn’t sure how to proceed. Thanks again.</p>
<p>Mastering factoring can require lots of practice for some, and is a confusing concept at first.</p>
<p>When factoring a quadratic equation, check if a is positive. If it is negative, multiply both sides of the equation by negative 1.</p>
<p>ex. -3x^2 +2x +2 ----> 3x^2-2x-2</p>
<p>next, list the factors a across from the factors of c, ignoring negatives
ex. x^2 + 2x + 1
-factors of a= 1,1
-factors of c=1,1</p>
<p>Now at this point, it gets tricky, and many different circumstances can happen, I will show you a simplified version.</p>
<p>set up two sets of parenthesis so that you have (?x+?)(?x+?).
Factors of a will be the question marks next to x, and factors of c will be question marks after the +. Our example limits the choices, making it much easier
so in our example x^2 + 2x + 1 = (x+1)(x+1)</p>
<p>The way factoring ties into the problem is when you calculate intercepts.</p>
<p>If y=0 then it is an x intercept AND one of the two terms in the equation written as a product(factored) must equal 0 - (0 times anything will equal 0)
So each part of the factored equation can be set equal to 0 and then solved for x
(x+1)(X+1)=0
x+1=0
x=-1</p>
<p>The SAT problem is just giving you the reverse. If you know that x-1 is a factor, then you know that y=0 when x=1 (the sign changes when you solve for x). When you substitute 1 into the problem, if it doesn’t equal 0, then you know that x-1 isn’t a factor, and therefore, the choice you are looking for</p>
<p>I see. Thanks a lot!</p>
<p>Now how do you figure out something like this in a timely manner
[Improve</a> Your SAT Scores with the SAT Skills Insight](<a href=“http://sat.collegeboard.com/practice/sat-skills-insight/math/band/600#skill0Example]Improve”>http://sat.collegeboard.com/practice/sat-skills-insight/math/band/600#skill0Example)</p>
<p>Ok, I haven’t done as much with sequences, but I’ll try to explain it.</p>
<p>First, in sequences, you can write the value of each term as a function of n (the term you are on). There are many different types of sequences, but if it says the difference between terms is constant that means it is arithmetic(i think)</p>
<p>basically this means in the equation that describes the sequence, there won’t be any powers to juggle.</p>
<p>In arithmetic sequences, you have a coefficient, n, and a constant. so it is ?n + or - ?
The coefficient of n is the difference between terms, so that is the best place to start.</p>
<p>You are given two terms, and their values. The difference between 4 and 11 (your terms) is 7. The difference between 47 and 19 (your values) is 28. To find the difference per term, divide 28 by 7 to get 4. (Think about slope of a line - it’s the same idea)</p>
<p>now you have 4n + ?. You are given a term and its value, so you can use substitution. When n is 4, your value is 19.
so 4(4) + ? =19
16+?=19
?=3</p>
<p>Now you can write your equation
value=4n+3</p>
<p>finally substitute 1 for n
value=4(1)+3
value=7</p>
<p>answer c</p>
<p>If you look at the process, it is just like finding the equation of a line given two points.
The difference between values is just like how much y increases when x increases by 1 (slope) the value you add is just like the y intercept, it shifts your starting value by its value.</p>
<p>Series can get much more complex than this, but for arithmetic series (I’m pretty sure that’s the name for it) it is a lot like finding the equation of a line.</p>