<p><a href="http://i42.tinypic.com/hvqwdl.png%5B/url%5D">http://i42.tinypic.com/hvqwdl.png</a></p>
<p>Please explain! Thanks</p>
<p>Woo! Finally got to one of these math help things before MIT guy…</p>
<p>Number 1:</p>
<p>First choose a small number for x (like 2), and plug it into both of the things they give you. Doing this, you get k=25, and the other part is 16. Then you can plug the k value you got (25) into all the answer choices, and see which one is 16. You get E.</p>
<p>Number 2:</p>
<p>Do the same thing you did for the first one. Choose a small number for x (like 2) and plug it into both parts. You get Y=4 and the other part is 8. Then plug in the Y value you got (4) into all the answer choices, and see which one equals 8. You get D.</p>
<p>This method (where you just use the answers to help you find the answer) is very helpful on the SAT, and using it, I guarantee, your score will increase. Good luck!</p>
<p>I wish I had the math skill to be able to go around helping everyone with math questions!! Thanks so much : )</p>
<p>Both can be solved algebraically in addition to plugging in numbers. I tend to prefer solving them algebraically since you don’t always guarantee obtaining the right answer after one try. Either method works, as long as you know you’ve eliminated four of the answers.</p>
<p>MITer: could you show me how to do it algebraically? Thats the method I tried (and incorrectly used).</p>
<ol>
<li><p>k^2 = x^2 + 6x + 9. Subtracting 9 from both sides, x^2 + 6x = k^2 - 9.</p></li>
<li><p>is a little tricky to do algebraically. Use the fact that 4^x = (2^2)^x = (2^x)^2 = y^2, and 2^(x+1) = 2*(2^x) = 2y, so 4^x - 2^(x+1) = y^2 - 2y.</p></li>
</ol>