document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1180749>Question 1180749</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Given the expression;  x2 - kx + 81\r<BR>\n" );
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document.write( "a) Determine the value of \"k\" that makes it a perfect square trinomial <BR>\n" );
document.write( "b) Factor it to prove it is factorable. </SPAN>\n" );
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document.write( "The first tutor carelessly provided an incomplete solution to the problem.<br><BR>\n" );
document.write( "The second tutor pompously provided a lengthy response full of wonderful math which unfortunately has nothing to do with the problem....<br><BR>\n" );
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document.write( "We need to find the value(s) of k that make x^2-kx+81 a perfect square:<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28x-a%29%5E2+=+x%5E2-2ax%2Ba%5E2+=+x%5E2-kx%2B81 ALIGN=MIDDLE  ALT=\"%28x-a%29%5E2+=+x%5E2-2ax%2Ba%5E2+=+x%5E2-kx%2B81\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "Equating the constant terms, we see a^2=81, which means a can be either 9 or -9.<br><BR>\n" );
document.write( "Then equating the linear terms, we see that k=2a, which makes k either 18 or -18.<br><BR>\n" );
document.write( "ANSWERS: k = 18 or k = -18<br><BR>\n" );
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