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3-46.

Use your knowledge of sigma notation to answer the following questions.

1. Expand: $\displaystyle \sum _ { i = 3 } ^ { 6 } ( 4 i ^ { 3 } - 1 )$

1. Start by evaluating the argument $(4i^3-1)$for $i=3$.
2. Continue to $i=6$.
3. Add all of the terms.

2. Write the following using sigma notation: $0.4\left(\frac{1}{2}+\frac{1}{2.4}+\frac{1}{2.8}+\frac{1}{3.2}+\frac{1}{3.6}\right)$

Start be determining an expression for the sequence $2$, $2.4$, $2.8$, $3.2$, $3.6$.