Answer: y = -9x+2000
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Step-by-step explanation:
x = number of minutes
y = amount of grain left over, in cubic meters
We can abbreviate "cubic meters" into "m^3" without quotes of course.
The silo holds 2000 m^3 of grain. This is the initial value, so it is the y intercept. This means b = 2000. If the silo wasn't completely full, then we'd have to use a different initial value.
The slope is -9 because the amount of grain decreases by 9 cubic meters per minute. We can think of it like
slope = rise/run = (change in y)/(change in x)
slope = (change in grain)/(change in time)
Saying slope = -9/1 means the change in grain is -9 m^3 and the change in time is 1 minute.
Because the slope is -9, we say that m = -9
Therefore, we go from y = mx+b to y = -9x+2000
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Note how plugging x = 0 into the equation leads to
y = -9x+2000
y = -9*0+2000
y = 0 + 2000
y = 2000
Showing that after 0 minutes, aka at the start, we have 2000 m^3 of grain.
Then at the x = 1 minute mark, we have...
y = -9x+2000
y = -9*1+2000
y = -9+2000
y = 1991
Showing that the silo lost 9 m^3 of grain since 2000-1991 = 9.
The graph y = -9x+2000 is a straight line that goes through the two points (0,2000) and (1,1991).