document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1186962>Question 1186962</A>: <I><SPAN STYLE=\"word-break: break-all;\"> An arithmetic sequence has first term a and common difference d. The sum of the first 25<BR>\n" );
document.write( "terms is 15 times the sum of the first 4 terms.<BR>\n" );
document.write( "a) Find a in terms of d.<BR>\n" );
document.write( "b) Find the 55th term in terms of a. </SPAN>\n" );
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document.write( "a)<br><BR>\n" );
document.write( "S(4) = (a)+(a+d)+(a+2d)+(a+3d) = 4a+(1+2+3)d = 4a+6d<br><BR>\n" );
document.write( "S(25) = (a)+(a+d)+(a+2d)+...+(a+23d)+(a+24d) = 25a+(1+2+...+23+24)d = 25a+300d<br><BR>\n" );
document.write( "S(25) is 15 times S(4):<br><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=25a%2B300d=15%284a%2B6d%29 ALIGN=MIDDLE  ALT=\"25a%2B300d=15%284a%2B6d%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=25a%2B300d=60a%2B90d ALIGN=MIDDLE  ALT=\"25a%2B300d=60a%2B90d\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=210d=35a ALIGN=MIDDLE  ALT=\"210d=35a\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a=210d%2F35 ALIGN=MIDDLE  ALT=\"a=210d%2F35\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a=6d ALIGN=MIDDLE  ALT=\"a=6d\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( "b) <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t%2855%29=a%2B54d+=+6d%2B54d+=+60d+=+10a ALIGN=MIDDLE  ALT=\"t%2855%29=a%2B54d+=+6d%2B54d+=+60d+=+10a\"   DISABLED_style= \"max-width:90%; height:auto;\" ><br><BR>\n" );
document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );