document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=188276>Question 188276</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Find a value for k that will make 4x^2 + 6.4 x + k a perfect square. Describe the procedure that you used which requires algebra [that is, not trial and error]. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #141132 by </B><A HREF=/tutors/aboutme.mpl?userid=Alan3354><B>Alan3354(69443)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Alan3354><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=Alan3354><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=141132\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Find a value for k that will make 4x^2 + 6.4 x + k a perfect square. Describe the procedure that you used which requires algebra [that is, not trial and error].<BR>\n" );
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document.write( "Make it easier by dividing by 4<BR>\n" );
document.write( "x^2 + 1.6x + k/4 = (x + c)^2<BR>\n" );
document.write( "x^2 + 1.6x + k/4 = x^2 + 2cx  + c^2<BR>\n" );
document.write( "The term k/4 is the coefficient of x, 1.6, divided by 2 and squared.<BR>\n" );
document.write( "c = 1.6/2 = 0.8<BR>\n" );
document.write( "k/4 = c^2 = 0.64<BR>\n" );
document.write( "k = 2.56<BR>\n" );
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document.write( "(2x + 1.6)^2 = 4x^2 + 6.4x + 2.56  looks good<BR>\n" );
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