Use the formula Sn =a (1 - rn ) ÷ (1 – r) to find the sum Sn for each of the infinite and finite geometric series. 9. The first 9 terms of 12, – 6 ,+ 3, - …

10. The first 15 terms of -1, + 1, -…

11. The first 6 terms of 1, + 3, + …

12. The first 10 terms of 2, – 4, + …

Asmall (but heavy) particle placed in a glass of water will follow a zigzag motion because the particle will bounce off of the water molecules it meets. this is called brownian motion. a physicist simulates this on a computer, by varying the distance a particle can travel (called the mean free length), on average, before it collides with a water molecule and assigning the change in motion to be one of 8 directions, each with a similar probability. by running the simulated particle (with the same mean free length) many times she determines that it should take 15 seconds, on average, for the particle to fall to the bottom, with a standard deviation of 1.5 seconds. next she lets a real particle fall through a glass of water and finds that it took 18 seconds. what does she conclude, and why?

Which of the following is the result of expanding

Which expression demonstrates the use of the commutative property of addition in the first step of simplifying the expression (-1+i)+(21+5i)+0