document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=309160>Question 309160</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The square of Mark's age 3 years ago is 6 times the age he will be in 9 years. What is his age now? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #221032 by </B><A HREF=/tutors/aboutme.mpl?userid=texttutoring><B>texttutoring(324)</B></A><img src=\"/images/stars/stars-10.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=texttutoring><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=texttutoring><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=221032\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The square of Mark's age 3 years ago\r<BR>\n" );
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document.write( "Let x = Mark's age now.\r<BR>\n" );
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document.write( "3 years ago, he was (x-3) years old. The square of his age 3 years ago is (x-3)^2\r<BR>\n" );
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document.write( "In 9 years (x+9), Mark will be 6 times the square of his (x-3) age.\r<BR>\n" );
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document.write( "(x-3)^2 = 6(x+9)<BR>\n" );
document.write( "(x^2-6x+9) = 6x+54<BR>\n" );
document.write( "x^2 - 12x -45 = 0\r<BR>\n" );
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document.write( "Factor this. Think what numbers multiply to -45 but add up to -12? -15 and 3.\r<BR>\n" );
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document.write( "(x-15)(x+3)=0\r<BR>\n" );
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document.write( "x=15, or x=-3\r<BR>\n" );
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document.write( "We can eliminate x=-3, because Mark can't have a negative age.\r<BR>\n" );
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document.write( "Mark is 15 years old now. </SPAN>\n" );
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