<p>On page 18 (Section 2), could somebody explain to me why 24 is D, as opposed to E? Thanks!</p>
<p>1.) y* = y^2 -1</p>
<p>2.) (y<em>)</em> = (y^2 -1)* (substituting y^2 -1 for y)</p>
<p>3.) ((y^2 -1)^2) -1 (substituting y^2 -1 for y in the above equation)</p>
<p>4.) y^4 -2y^2 +1 -1 (distribute)</p>
<p>5.) y^4 -2y^2 (+1 and -1 cancel)</p>
<p>So the answer is indeed D. If you chose E, it might be because you forgot to include the -1 term (outside the parentheses) in step 3. I hope that makes sense. You know how hard it is to write math problems on here…</p>
<p>You may want to do this one by plugging in a number. For example, if you let y = 2, then y* = 2^2 - 1 = 4 - 1 = 3, and (y<em>)</em> = 3* = 3^2 - 1 = 9 - 1 = 8. Put a nice, big dark circle around the number 8.</p>
<p>Now substitute 2 in for y in each answer choice:</p>
<p>(A) 2^4 - 1 = 15
(B) 2^4 - 2^2 - 1 = 11
(C) 2^4 + 2^2 - 1 = 19
(D) 2^4 -2(2^2) = 8
(E) 2^4 - 2(2^2) + 1 = 9</p>
<p>Since (A),(B),(C), and (E) came out incorrect we can eliminate them. Therefore the answer is choice (D).</p>