Sum of n terms in a geometric progression is given by Sn = a1 (1 - r^n) / (1 -r)
3( 1 - 4^6) / (1-4)
= 4,095
For question 4 the answer is yes and for question 5 the answer is false
D = 20 , v = 19
20v + 12d - 6v
= 20 (19) + 12 (20) - 6 (19)
= 380 + 240 - 114
= 620 - 114
= 506
When d = 20 and v = 19
20v + 12d - 6v = 506
X= -9.375. 0.06x-0.14x=13.48-12.73. -0.08x=0.75