whatevs Group Title Need help on thiss 2 years ago 2 years ago

1. whatevs Group Title

2. FoolForMath Group Title

-28

3. whatevs Group Title

how did you solve it...i have 5 more problems like this..

4. whatevs Group Title

is there a way to put it into wolfram?

5. FoolForMath Group Title

I looked at it then I thought of a number.

6. FoolForMath Group Title
7. whatevs Group Title

can you help me with these kind of problems?

8. FoolForMath Group Title

Sure.

9. whatevs Group Title

Given the sequence 9, 12, 15, which of the following is equivalent to

10. whatevs Group Title

thanks aloot..

11. mathmate Group Title

You can split the summations, and evaluate each one separately. $\sum_{4}^{7}-2n+4 = \sum_{4}^{7}-2n + \sum_{4}^{7}4$ $= -2\sum_{4}^{7}n + 4\sum_{4}^{7} 1$ $= -2(\sum_{1}^{7}n - \sum_{1}^{3}n ) + 4(4)$ $= -2[ 7(7+1)/2 - 3(3+1)/2 ] - 16$ $= -44 + 16$ $= -28$