Here we use the equation
[tex] y = a(b)^x [/tex]
Taking points (0,4), (1,2)
Substituting the point (0,4) , we will get
[tex] 4 = a(b)^0
\\
4 = a(1) \\
a =4 [/tex]
Substituting (1,2) we will get
[tex] 2 = 4 (b)^1
\\
2/4 = b
\\
b = 1/2 [/tex]
So we have
[tex] a = 4, b = 1/2 [/tex]
Therefore , required equation is
[tex] y = 4(1/2)^x [/tex]
