Question

用配方法证明,代数式-3x²-x+1的值不大于13/12

Answer 1

证明：

-3x²-x+1

=-3(x²+1/3x)+1

=-3(x²+1/3x+1/36)+1/12+1

=-3(x+1/6)²+13/12

因为-3(x+1/6)²≤0,所以-3(x+1/6)²+13/12≤13/12

所以

-3x²-x+1的值不大于13/12