问题
填空题
用配方法使下面等式成立: (1)x2-2x-3=(x-______)2-______; (2)x2+0.4x+0.5=(x+______)2+______; (3)3x2+2x-2=3(x+______)2+______; (4)
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答案
(1)x2-2x-3=x2-2x+1-4=(x-1)2-4;
故答案为:1,4
(2)x2+0.4x+0.5=x2+0.4x+0.04+0.46=(x+0.2)2+0.46;
故答案为:0.2,0.46
(3)3x2+2x-2=3(x2+
x)-2=3(x2+2 3
x+2 3
)-1 9
=3(x+7 3
)2-1 3
;7 3
故答案为:
,-1 3
;7 3
(4)
x2+2 3
x-2=1 3
(x2+2 3
x)-2=1 2
(x2+2 3
x+1 2
)-1 4
=49 24
(x+2 3
)2-1 4
;49 24
故答案为:
,-1 4
.49 24