Y=1.5 at the midpoint of GH. To do this you add the y values of the endpoints together and divide by two ----> 5-2= 3 ----> 3/2= 1.5
Hope this helps you !!
ΔACD is similar to ΔBCD by AA similarity theorem
AD/AC = BD/BC
x/5 = 4.2/6
6x = 21
x = 3.5
Hope this helps! ;)

bearing in mind that, the geometric sequence is "convergent" only when |r|<1, or namely "r" is a fraction between 0 and 1.
The answer is (x,y) = (-2, 16)
do you need an explanation as well?