化简求值
求y=根号下x方-x-6的最值
y=√[(x^2-x+1/4)-1/4-6] =√[x-1/2)^2-25/4] [x-1/2)^2-25/4]>=0 (x-1/2)^2>=25/4=(5/2)^2 x-1/2>=5/2 x>=3 或 x-1/2>=-5/2 x>=-2 当 x=3或x=-2时 y有最值0
答:(1)甲的解答是错误的; (2)错误的解答在于未能正确运用二次根式的性质: √a=-a,(当a<0) (3)化简并求值|1-a|+√(1-8a+16a²...详情>>
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