<p>Let's make a list of the hard questions on Barron's and how to solve them by hand or by using a TI89.</p>
<p>This question is a hard one...that I don't understand Barron's reasoning.</p>
<p>What's your answer? I got B, but the answer is D.</p>
<p>Hmm..well I got answer C. I'm probably totally wrong and that is the "obvious" answer, so if anyone has the solution to find D, I would appreciate that too.</p>
<p>This is a good thread- I will be sure to add some questions in the next few days.</p>
<p>What I did is this:</p>
<p>original function
y=sqrt(1-x^2)
y=-sqrt(1-x^2)</p>
<p>changed function
y=sqrt(1-(2x)^2)
y=-sqrt(1-(2x)^2)</p>
<p>i really dont know... i just saw 2x and x so you would assume that you just double the width of it which would be c. it doesnt make a lot of sense to me.</p>
<p>Next question:</p>
<p>When (1-(1/x))^-6 is expanded, the sume of the last three coefficients is</p>
<p>A) 10
B) 11
C) 16
D) -11
E) The sum cannot be determined.</p>
<p>According to Mr TI89 over here:</p>
<p>expand((1-(1/x)^-6),x) = 6/(x-1) + 15/(x-2)^2 + 20/(x-1)^3 + 15/(x-1)^4 + 6/(x-1)^5 + 1/(x-1)^6 + 1</p>
<p>If you add the last three coefficients, you get 1+1+6=8, which is not a choice.</p>
<p>CORRECT ANSWER: E, when you have a thing raised to a negative exponent, the expansion goes on forever.</p>
<p>Next question:</p>
<p>If 5 and -1 are both zeros of the polynomial P(x), then a factor of P(x) is</p>
<p>A) x^2-5
B) x^2-4x+5
C) x^2+4x-5
D) x^2+5
E) x^2-4x-5</p>
<p>CORRECT ANSWER: C - (x+5) and (x-1) are factors. Don't ask me how they got their answer.</p>
<p>Next question:</p>
<p>The length of the radius of the sphere x^2+y^2+z^2+2x+4y=10 is
A) 3.16
B) 3.38
C) 3.87
D) 3.74
E) 3.46</p>
<p>CORRECT ANSWER: C.</p>
<p>Please explain how you did it using the TI89 or an easy way by hand.</p>
<p>Next question:</p>
<p>If f is a linear function and f(-2)=11, f(5)=-2, and the f(x)=4.3, what is the value of x?</p>
<p>A) 3.2
B) -1.9
C) 2.9
D) 1.6
E) -3.1</p>
<p>CORRECT ANSWER: D. I know how to figure it out using good old algebra, but is there an easier way to do this with a TI 89?</p>
<p>Next question:</p>
<p>A unit vector parallel to vector V (->) = (2, -3.6) is a vector</p>
<p>A) (-2,3,-6)
B) (6, -3, 2)
C) (-.29, .43, -.86)
D) (.29, .43, -.86)
E) (-.36, -.54, 1.08)</p>
<p>CORRECT ANSWER: C. Please explain. I'm totally lost.</p>
<p>Next question:</p>
<p>If f(x) = ax^2+bx+c, how must a and b be related so the the graph of f(x-3) will be symmetric about the y-axis?</p>
<p>A) a=b
B) b=0, a is any real number
C) b=3a
D) b=6a
E) a = (1/9)b</p>
<p>How I did it:
- For y-axis symmetry, you have to have f(x) = f(-x).
- Solve for f(x-3)
a(x-3)^2 - b(x-3) + c = a(-x-3)^2 - b(-x-3) + c
a(x^2-9) - bx + 3b + c = a(x^2+9) + bx + c
ax^2 - 9a - bx + 3b + c = ax^2 + 9a + bx + c
-bx = bx</p>
<p>Solve -bx = bx for b and you'll get b=-b. The only solution for that is b=0.</p>
<p>But B is not the answer.</p>
<p>CORRECT ANSWER: D. Please explain.</p>
<p>I created a list of useful programs at <a href="http://www.sendspace.com/file/jlqiwb%5B/url%5D">http://www.sendspace.com/file/jlqiwb</a>. It includes finding the equation of a line with two points, etc.</p>
<p>why would you bother solving barron's problems -_-</p>
<p>I've heard that after you practice with Barrons, the real SAT II is really easy.</p>
<p>i don't see how practicing with problems that aren't even related to the test helps, but okay i guess</p>
<p>Can you explain how you did the linear equation problem by hand?</p>
<p>
[quote]
i don't see how practicing with problems that aren't even related to the test helps, but okay i guess
[/quote]
</p>
<p>Are you saying that these questions cover material that isn't on the test? They seem like questions that can be solved using algebra.</p>
<p>
[quote]
Can you explain how you did the linear equation problem by hand?
[/quote]
</p>
<p>You can figure it out using the function linepq({-2,11},{5,-2]). That will spit out the equation of the line. Use that equation with solve() by setting the equation equal to 0.</p>
<p>The function linepq() can be found in one of my earlier posts.</p>
<p>dude these problems are really hard... i dont think the real test will be so difficult</p>
<p>
[quote]
dude these problems are really hard... i dont think the real test will be so difficult
[/quote]
</p>
<p>I know they're hard, which is why I have to figure out a way to solve them. Last June, I did well on practice tests (710, 750, 770, 790 - PR, CB Real SAT Subject, SparkNotes), and I ended up with a 660 on the real thing.</p>