document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=190319>Question 190319</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Please help me by answering this question: why minus and minus makes plus?<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #142859 by </B><A HREF=/tutors/aboutme.mpl?userid=edjones><B>edjones(8007)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=edjones><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=edjones><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=142859\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Please help me by answering this question: why minus and minus makes plus?<BR>\n" );
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document.write( "Proof:<BR>\n" );
document.write( "Let a and b be any real numbers.<BR>\n" );
document.write( "Let x=ab+(-a)(b)+(-a)(-b)<BR>\n" );
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document.write( "x= ab+(-a)[(b)+(-b)] factor out -a<BR>\n" );
document.write( "=ab+(-a)(0)<BR>\n" );
document.write( "=ab+0<BR>\n" );
document.write( "=ab<BR>\n" );
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document.write( "x=[a+(-a)]b+(-a)(-b)  factor out b<BR>\n" );
document.write( "=0*b+(-a)(-b)<BR>\n" );
document.write( "=0+(-a)(-b)<BR>\n" );
document.write( "=(-a)(-b)<BR>\n" );
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document.write( "x=ab=(-a)(-b)<BR>\n" );
document.write( "So, (-a)(-b)=ab<BR>\n" );
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document.write( "Ed\r<BR>\n" );
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