Question 190549
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Remember Problem # <font color=blue>189853?</font> It is the same as this one right?


You were just looking a straight Line formula, <font color=blue>Ax + By + C =0 </font> and we we'll get there. The double interpolation we did is also one way of doing it.




Let <font color=blue>x</font> = Year and <font color=blue>y</font> = Sales:


If x = 0 for year 1990, then y = 140.5. This makes our Line Eq'n,---> <font color=green>x + y =140.5</font>.


If x = 10 for year 2000, then y = 180.5. This makes our Line Eqn, ---> <font color=red> -4x + y =140.5 </font>. Why?


Let's substitute x=10:


{{{-4(10) + y =140.5}}}
{{{-40+y=140.5}}}
{{{y=140.5+40=red(180.5)}}}, correct.



Therefore, to find for Sales for the year 1997:


We use x=7 for year 1997:
{{{-4(highlight(7))+y=140.5}}}
{{{-28+y=140.5}}}
{{{y=140.5+28=highlight(red(168.50))}}}, Sales for 1997



To find Sales for 2003, we use x=13:
{{{-4(highlight(13))+y=140.5}}}
{{{-52+y=140.5}}}
y=140.5+52=192.50, Sales for 2003



See Problem 189853 again, the values are the same. There is a misprint but it was adjusted.


Your working Line Eqn, -4x + y =140.5 ( Answer )



Thank you,
Jojo