若代数式x2+1的值是5，则代数式3x2+1的值是__________．

若代数式x²+1的值是5，则代数式3x²+1的值是__________．

答案

13．

【考点】代数式求值．

【专题】计算题；实数．

【分析】根据已知代数式的值求出x²的值，代入原式计算即可得到结果．

【解答】解：∵x²+1=5，

∴x²=4，

则原式=12+1=13．

故答案为：13．

【点评】此题考查了代数式求值，熟练掌握运算法则是解本题的关键．

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