不等式8x^4+8(a-2)x^2 -a+5>0的解集为R,则a的取值范围是?A.(1/2,5) B.(-无穷,2) C.(2,+无穷) D.(2,5)
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不等式8x^4+8(a-2)x^2 -a+5>0的解集为R,则a的取值范围是?A.(1/2,5) B.(-无穷,2) C.(2,+无穷) D.(2,5)
不等式8x^4+8(a-2)x^2 -a+5>0的解集为R,则a的取值范围是?
A.(1/2,5) B.(-无穷,2) C.(2,+无穷) D.(2,5)
不等式8x^4+8(a-2)x^2 -a+5>0的解集为R,则a的取值范围是?A.(1/2,5) B.(-无穷,2) C.(2,+无穷) D.(2,5)
f(x)=8x^4+8(a-2)x^2 -a+5>0
取x=0,直接排除C
取x=1,f(1)=8+8(a-2)-a+5=7a-3,排除B
取a=1,f(x)=8x^4-8x^2 +4=8(x^2-1/2)^2+2>0,排除D
答案是A,选择题做法灵巧一点,不需要复杂的过程