The first four terms of an arithmetic sequence are: 6 10 14 18
a) Show that the sum to n terms can be written as 2n2 + 4n.
b) If the sum to n terms is 880, write a quadratic equation to represent this information. Rearrange to equal 0 and plot a graph of this equation on your GDC. Hence, sketch the graph on paper, showing the coordinates of the vertex and axes intercepts.
c) Find the positive x-intercept.
d) State what information the positive x-intercept tells you about the sequence.