(* Authors: Albert Qiaochu Jiang *) theory mathd_algebra_616 imports Complex_Main begin theorem mathd_algebra_616: fixes f g :: "real \ real" assumes h0 : "\x. f x = x^3 + 2 * x + 1" and h1 : "\x. g x = x - 1" shows "f (g 1) = 1" proof - have "g 1 = 0" using h1[of 1] by simp then show ?thesis using h0[of "(g 1)"] by simp qed end