c(1)=−20 c(n)=c(n−1)+10 find the 2nd term in the sequence.

-10 is the second term.

Step-by-step explanation:

After the first term each term is obtained from the previous one by adding 10.

c(1) = -20

so c(2) = -20 + 10

= -10.

I can use variables to represent the coordinates of the vertices for a general triangle, ∆ABC. Then I can calculate the midpoints of the sides in terms of those variables. Using the point-slope formula for the equation of a straight line, I can build the symbolic equations for the three medians, AE, BF, and CD. I can solve for the point of intersection for two of the medians, AE and BF, for example. Finally, I can prove the lines (i.e., medians) concurrent if the point I found also satisfies the equation of the line for CD.