<p>This is the official thread of SAT Math Questions, where you can post questions that you don't understand and also help others.</p>
<p>I'll start off with the first.</p>
<p>In the xy-plane, line l passes through the origin and is perpendicular to the line 4x+y=k, where k is a constant. If the two lines intersect at point (t, t+1), what is the value of t?</p>
<p>I use y=mx+b form
pass through origin -> b is 0
perpendicular to the line 4x+y=k -> m=1/4</p>
<p>Then you have: y=1/4x, y=-4x+k intersecting at (t,t+1) -> solution for both
t+1=t/4 at this point t is separated and by itself. So t = -4/3.
If the question asked for the value of k. The information 'intersection' would have been used.</p>
<p>I thought it's asking for the value of T in terms of K. What I did was got the slope of the 4x + y = k line to be -4 so the perpendicular line has slope of 1/4. The equation for perpendicular line that passes through (0,0) is y-0=1/4(x-0) which is just y = 1/4x. </p>
<p>I then changed the 4x + y = K into slope intercept which is y = -4x + K. I made the two values of y equal to each other. I got 1/4x = -4x + k. That's the same as x = -16x + 4k (multiplying everything by 4 to get rid of fraction). I added the 16x and get 17x = 4k. x = 4k/17. So my point of intersection was (4k/17, 4k/17 + 1). Not sure what I'm doing wrong.</p>
<p>so my answer for t is 4k/17</p>
<p>Oh, thanks guys! By the way, the answer is t= -4/3</p>
<p>I would like to buy a graph calculator, now I am considering the TI83 and the TI89, what are the differences and which one should I pick</p>
<p>and what about the 84+</p>
<p>Buy the TI-83.</p>
<p>Simply because the TI-89 cannot be used in any standarized tests that allow or require calculators including SAT, ACT, and AP.</p>
<p>However, you can also buy the TI-84 but the only difference is that it simply has more memory (very little in comparison) than its predecessor, the
TI-83.</p>
<p>Hope that helped</p>
<p>At this point, I have the Casio cfx-9850GB, but the problem is that I haven't found a place where it's explained how I must write for example the Midpoint or distance programs. While for Ti-83 I found several sites, so thats why I am not considering to buy a new Grapcalc</p>
<p>TI-89 is allowed in SAT, AP, and PSAT Assessments.</p>
<p>TI-89 can be used in SAT but not in ACT. So you might want to get a TI-83.</p>
<p>Is it worth buy the Ti-83 if you already have the graph calc casiocfx 9850?</p>
<p>It is really worth to buy the TI-89, trinya. Although you cannot use it for the ACT, the level of the questions in the math part of the ACT is easy, and as such, your casiofx 9850 will suffice. If you're going to take SAT IIs and/or AP Calc or Phys, I strongly recommened the TI-89.</p>
<p>Not familiar with casiocfx 9850, but I am familiar with TI-83 plus and TI-89 titanium calculators and TI-83 and TI-89 are both great calculators.</p>
<p>Man, I am seriously mathematically challenged, lol.</p>
<p>1.
If a and b are positive integers and (a^1/2 * b^1/3)^6 = 432, what is the value of ab?
a. 6
b. 12
c. 18
d. 24
e. 36</p>
<p>2.
A school ordered $600 worth of lightbulbs. Some of the lightbulbs cost $1 each and the others cost $2 eac. If twice as many $1 bulbs as $2 bulbs were ordered, how many lightbulbs were ordered altogether?</p>
<p>never mind about number 2, heh.</p>
<p>1.
so (a^3)(b^2)=432
You just factor 432.
It comes out to (3^3)(2^4)
2^4 =(2^2)^2=(4)^2
so a=3
and b=4
ab=12.
BTW, the 89 has a factoring function for this exact problem. You type in the number and it gives the prime factors. There are programs like that for the 83 also.</p>
<h1>2 is 450 right?</h1>
<h1>2 is 450 I got that as well.</h1>
<p>Yup, #2 is 450</p>
<p>You know how how to do the factoring on the 83?</p>
<p>sadly, no function exists. </p>
<p>correct me if i'm wrong. i want to be wrong.</p>