isabelle/valid/amc12b_2003_p9.thy (13 lines of code) (raw):

(* Authors: Wenda Li *) theory amc12b_2003_p9 imports Complex_Main begin theorem amc12b_2003_p9: fixes a b ::real and f :: "real \<Rightarrow> real" assumes "\<forall> x. f x = a * x + b" and " f 6 - f 2 = 12" shows "f 12 - f 2 = 30" using assms by auto end