Let X and Y be the year and sales.
There are four known values of y.
So, using binominal expansion;
(y-1)4 = 0 : y4<-4y3 + 6y2-4y1 + yo = 0 ……….. (1)
130-4 (76)+ 6(50)-4 y1 + 26 = 0
130-304 +300-4y1 + 26 = 0
152 – 4y1 = 0
∴ -y1= -152/4 y1 = 38
Rewrite equation (1) by increasing suffixes of by ‘ 1’ we get y5
y5 – 4y4 + 6y3 – 4y2 + y1=0
y5 – 4(130) + 6(76) – 4(50) + 38 = 0;
Since y1 = 38
y5 – 520 + 456 – 200 + 38 = 0
∴ y5 = 226.
