Task 1 the sum Sn of a finite arithmetic series of n terms is Sn=n/2(a1+an) where a1 is the first term and an is the nth term

a. the sum Sn of a finite arithmetic series of n terms is Sn=n/2(a1+an) where a1 is the first term and an is the nth term
b. explain why Sn=na1+n(n-1)/2 d makes sense by explaining how you can extract each of na1 and n(n-1)/2 d from the sum a1+(a1+d)+(a1+2d)+...+(a1+(n-1)d)

Is there a direction u in which the rate of change of f(x, y)equals=x squared minus 3 xy plus 4 y squaredx2−3xy+4y2 at p(1,2) equals 14? give reasons for your answer. choose the correct answer below. a. no. the given rate of change is smaller than the minimum rate of change. b. no. the given rate of change is larger than the maximum rate of change. c. yes. the given rate of change is larger than the minimum rate of change and smaller than the maximum rate of change.