PATTERNS, FUR1 2008 VCAA 3 MC

The values of the first seven terms of a geometric sequence are plotted on the graph above.
Values of `a` and `r` that could apply to this sequence are respectively

(A) `a=90`	`\ \ \ \ r= – 0.9`
(B) `a=100`	`\ \ \ \ r= – 0.9`
(C) `a=100`	`\ \ \ \ r= – 0.8`
(D) `a=100`	`\ \ \ \ r=0.8`
(E) `a=90`	`\ \ \ \ r=0.9`

Show Answers Only

`B`

Show Worked Solution

`text(By elimination,)`

`T_1=a=100`

`text(Eliminate A and E.)`

`T_2=ar`	`=-90`
`:.100r`	`=-90`
`r`	`=-0.90`

`text(Eliminate C and D.)`

`=> B`