Question 1144178
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..., weight of a plane is a linear function of the amount of fuel in its tank. When carrying 15 gallons of fuel, the airplane weighs 1987 pounds. When carrying 40 gallons of fuel, it weighs 2132 pounds. 
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Two points of a line, (15,1987) & (40,2132).
(x,y) points


{{{y-2132=((2132-1987)/(40-15))(x-40)}}}, using point-slope form;


{{{y=(5&4/5)(x-40)+2132}}}

{{{y=5.8x-232+2132}}}

{{{highlight_green(y=5.8x+1900)}}}


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How much does the airplane weight if it is carrying 50 gallons of fuel ?
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Let x equal 50, and evaluate y.