Browse · MATH Print → jmc algebra intermediate Problem A function f has the property that f(3x−1)=x2+x+1 for all real numbers x. What is f(5)? Solution — click to reveal Let u=3x−1. Then x=(u+1)/3, and f(u)=(3u+1)2+3u+1+1=9u2+2u+1+3u+1+1=9u2+5u+13.In particular, f(5)=952+5⋅5+13=963=7. Final answer 7 ← Previous problem Next problem →