document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=950421>Question 950421</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In a proof of 1 + 2 +3+ ... + n = n(n+1)/2 by mathematical induction, an appropriate first step is to prove which of these statements?<BR>\n" );
document.write( " a. 1=1(1+1)/2<BR>\n" );
document.write( "b.1+2=1+n<BR>\n" );
document.write( "c. 1=n(n+1)/2<BR>\n" );
document.write( "d. 1+n=n(n+1)/2 </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #580383 by </B><A HREF=/tutors/aboutme.mpl?userid=KMST><B>KMST(5328)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=KMST><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=KMST><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=580383\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The first step I'd always to prove that the formula/equation is true for n=1, so there should be no n in your first step.<BR>\n" );
document.write( "That disqualifies choices b, c, and d, so it must be a.<BR>\n" );
document.write( "Also, substituting 1 for n in that formula tells you that the sum of the first 1 natural numbers,<BR>\n" );
document.write( "from 1 to n=1, which is just 1,<BR>\n" );
document.write( "is equal to 1(1+1)/2. </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );