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<a href="http://i40.tinypic.com/29p3n0h.jpg%5B/IMG%5D">http://i40.tinypic.com/29p3n0h.jpg
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<p>E) -5</p>
<p>The question is nothing like the questions I've seen from official previous SAT/PSAT tests. Would I be expected to see something like this on the actual tests?</p>
<p>This question does not seem too strange… and it doesn’t require too many steps (especially if you have a CAS calculator)</p>
<p>Since the question states “for all real values of x except -5/4”, just plug in 1 for x (the easiest number to use)</p>
<p>and since f(f(x)) = x, you know that since we used (plugged in 1)</p>
<p>(hereon forth let x mean times/multiplication) </p>
<p>1 = (k x (k/8)) / (3 x (k/8) +5)</p>
<p>1 = (k^2) / 3k +40</p>
<p>3k + 40 = k^2</p>
<p>k^2 - 3k - 40 = 0</p>
<p>factor…</p>
<p>(k - 8)(k + 5) =0</p>
<p>therefore, to satisfy the equation, k must be 8 or -5. </p>
<p>I think this kind of question is fair game on the sat. - but maybe one of the last few questions (harder ones)</p>
<p>so is the answer A?</p>
<p>that’d be my best guess.</p>
<p>I solved it the same way Lipp7260 did and got k=8 and k=-5. What is the correct answer?</p>
<p>damn, The question isn’t strange but the answer choices are</p>
<p>E) -5 is half right … but it can also be 8, meaning A) is right too.</p>
<p>…damn.</p>
<p>actually, I don’t know what I would put as an answer…</p>
<p>I don’t think half right counts so it’s A since k cannot be uniquely determined</p>
<p>^ what i thought originally.</p>
