Rakesh and Tessa were asked to find an explicit formula for the sequence 100\,,\,50\,,\,25\,,\,12.5,...100,5 0,25,12.5,...100, comma, 50, comma, 25, comma, 12, point, 5, comma, point, point, point, where the first term should be f(1)f(1)f, left parenthesis, 1, right parenthesis. Rakesh said the formula is f(n)=100\cdot\left(\dfrac{1}{2}\rig ht)^{{n-1}}f(n)=100⋅(
2
1
​
)
n−1
f, left parenthesis, n, right parenthesis, equals, 100, dot, left parenthesis, start fraction, 1, divided by, 2, end fraction, right parenthesis, start superscript, n, minus, 1, end superscript, and
Tessa said the formula is f(n)=200\cdot\left(\dfrac{1}{2}\rig ht)^{{n}}f(n)=200⋅(
2
1
​
)
n
f, left parenthesis, n, right parenthesis, equals, 200, dot, left parenthesis, start fraction, 1, divided by, 2, end fraction, right parenthesis, start superscript, n, end superscript.
Which one of them is right?