Finding the rule of a mapping 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=5 y=5+(x−1)d The d is the interval between each consecutive y In this mapping, d=8−5=11−8=14−11=17−14=3 We can substitute our d and simplify the expression for y y=5+(x−1)d y=5+(x−1)3 y=5+3×x−1×3 y=5+3x−3 y=5−3+3x y=2+3x y=3x+2 y⟶3x+2