Guys i nd with my algebra i need 2 and 4

Which is an equation for the nth terms of the sequence 12,15,18,21

(a) compute the maclaurin polynomial m2(x) for f(x) = cos x. (b) use the polynomial of part (a) to estimate cos π 12. (c) use a calculator to compute the error made using the estimate from part (b) for the value of cos π 12. remember that the error is defined to be the absolute value of the difference between the true value and the estimate.

Assume that y varies inversely with x. if y=1.6 when x=0.5 find x when y=3.2 acellus answer