求思路和过程,谢谢
3个回答
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(1) a²-a+1=a²-a+1/4+3/4=(a-1/2)²+3/4
(a-1/2)²>=0 (a-1/2)²+3/4>0 即原式恒大天0
(2) -9x²+8x-2=-9(x²-8/9x+16/81)+16/9-2
=-9(x-4/9)²-2/9
(x-4/9)²>=0 -9(x-4/9)²<=0
-9(x-4/9)²-2/9<0 即原式恒小于0
(3) -3x²+12x-16=-3(x²-4x+4)+12-16
=-3(x-2)²-4
(x-2)²>=0 -3(x-2)²<=0
-3(x-2)²-4<0 即原式恒小于0
(a-1/2)²>=0 (a-1/2)²+3/4>0 即原式恒大天0
(2) -9x²+8x-2=-9(x²-8/9x+16/81)+16/9-2
=-9(x-4/9)²-2/9
(x-4/9)²>=0 -9(x-4/9)²<=0
-9(x-4/9)²-2/9<0 即原式恒小于0
(3) -3x²+12x-16=-3(x²-4x+4)+12-16
=-3(x-2)²-4
(x-2)²>=0 -3(x-2)²<=0
-3(x-2)²-4<0 即原式恒小于0
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