<u>Understanding:</u>
The sum of a geometric series is, , with a being the start point and r is the common ratio. We can also use the following formula to make life easier
, a is your start point, r is the common ratio, and n is the number of terms, which in our case is S7.
<u>Solution:</u>
Our start point is 1, ,
The common ratio is 5, ,
And finally, the number of terms is 7, .
The answer is [A] 19531.
Please find the question attached below.
The equation that models the decrease in water (in gallons) of the fish tank over time (in hours) is y = - 20x + 180.
We know that a linear equation with one variable is one that contains just one variable.
Here we have to find the appropriate equation that models the given chart.
For option A. :
y = - 40x + 140
At x = 2, y = - 40*2 + 140 = - 80 + 140 = 60 =/ 140
So this option is incorrect.
For option B.:
y = - 40x + 180
At x = 2, y = - 40*2 + 180 = - 80 + 180 = 100 =/ 140
So this option is incorrect.
For option C.:
y = - 20x + 140
At x = 2, y = - 20*2 + 140 = - 40 + 140 = 100 =/ 140
So this option is incorrect.
For option D.:
y = - 20x + 180
At x = 2, y = - 20*2 + 180 = - 40 + 180 = 140
So this option is correct.
Therefore, the equation that models the decrease in water (in gallons) of the fish tank over time (in hours) is y = - 20x + 180. So, the last option is correct.
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