Note: If the mapping has equal interval (difference) for the y and x interval of 1 , you can use the general linear sequence formula to find the rule of the mapping. Un=U1+(n−1)d In the mapping, Un=y and n=x and U1, the first value of y U1=4 y=4+(x−1)d The d is the interval between each consecutive y In this mapping, d=2−4=0−2=−2−0=−4−(−2)=−2 We can substitute our d and simplify the expression for y y=4+(x−1)d y=4+(x−1)(−2) y=4+−2×x−1×−2 y=4+−2x+2 y=4+2−2x y=6+−2x y=−2x+6