Very confused, please help

What is the common difference in the following arithmetic sequence? 7,3,-1,-5

What are the critical values that correspond to a 95% confidence level and a sample size of 93? a. 65.647, 118.136 b. 59.196, 128.299 c. 57.143, 106.629 d. 69.196, 113.145

In each of the cases that follow, the magnitude of a vector is given along with the counterclockwise angle it makes with the +x axis. use trigonometry to find the x and y components of the vector. also, sketch each vector approximately to scale to see if your calculated answers seem reasonable. (a) 50.0 n at 60.0°, (b) 75 m/ s at 5π/ 6 rad, (c) 254 lb at 325°, (d) 69 km at 1.1π rad.