MagpiesFreak7
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Arithmetic Sequences HELP! (1 Viewer)
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MagpiesFreak7
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Question 8 please
TheMathStudent
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Keep in mind that the general equation for Sum is:
d) \\
S_n & =\frac{na+n^2 d -nd}{2} \\
S_n &=n^2 \frac{d}{2}+ n\frac{(a-d)}{2}\equiv n^2 - 3n \\
\therefore & \frac{d}{2}=1, \qquad \frac{(a-d)}{2}=-3
\end{align*}
)
I'll assume you can solve the last line with simultaneous equations
I'll assume you can solve the last line with simultaneous equations