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《中学生数学》2 0 0 1年第 1 1月上期所登《解题时切勿忘了“Δ”》一文中的例 2是 :例 2求ｙ=ｘ + 4( 1 - ｘ2 ) 2 + 1的范围 (ｘ∈Ｒ) .简解 将 ｙ =ｘ + 4( 1 - ｘ2 ) 2 + 1 移项平方后得3ｘ2 - ( 1 6- 2ｙ)ｘ - ｙ2 + 3 2 =0 .∴ Δ =( 1 6- 2 ｙ) 2 - 1 2 ( - ｙ2 + 3
“Secondary students mathematics” in the first month of January 2001, “Don’t forget about ”Δ“ when solving a problem.” Example 2 is: Example 2 Find y=x + 4( 1 - x2 ) 2 + The range of 1 (x ∈ R). A simple solution will be y = x + 4 (1 - x2) 2 + 1 after shifting the square to get 3x2 - (1 6 - 2y) x - y2 + 3 2 =0 .∴ Δ = ( 1 6- 2 y) 2 - 1 2 ( - y2 + 3