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1. A fuel is purified by passing it through a clay pipe. Each foot of the clay pipe removes a fixed percentage of impurities in the fuel. Let f(x) represent the amount of pollutants, in tons, left in the fuel after it had passed through x feet of the clay pipe.

f(x) = 10(0.8)^x

What does the number 0.8 represent?

Every foot of the pipe keeps 80% of the pollutant.
Every foot of the pipe removes 80% of the pollutant.
The original amount of pollutant present in the fuel was 80 tons.
The original amount of pollutant present in the fuel was 20 tons.

2. Choose the equation below that represents the line passing through the point (2, −4) with a slope of one half.

y = one halfx + 5
y = one halfx − 3
y = one halfx − 5
y = one halfx + 3

Respuesta :

wuzzleluver
1. Well, we know it cannot be either the last or second to last answer as the original amount of pollutant (when x=0) is 10 tons. 
After 1 foot of pipe 8 tons of pollutant are left (x=1). 8 tons is 80% of the original amount of the pollutant present. So, each foot of pipe keeps 80% of the pollutant. Make sense?

2. Just plug in the point into each answer choice.
(2,4)
y= 0.5x+ 5
4=0.5(2)+5
4=6
which is not true therefore the first answer choice is incorrect. 

y=0.5x -3
4=0.5(2)-3
4=1-3
4=2
which is not true therefore the first answer choice is incorrect. 

y=0.5x-5
4=0.5(2)-5
4=-4
which is not true therefore the first answer choice is incorrect. 

y=0.5x +3
4=0.5(2)+3
4=1+3
4=4
This is the correct answer.

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