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Posted by U15248702 (U15248702) on Tuesday, 1st May 2012
Could someone please explain to me how you work out question 12b in 2011's credit paper 1.
Posted by Maths Teacher BBC (U15178780) on Wednesday, 2nd May 2012
Look at the pattern:
S4 = ½ ( 4 x 5)
So substitute for n:
Sn = ½ ( n x (n+1))
Now multiply out the brackets:
Sn = ½ ( n² + n)
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