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幼苗
共回答了19个问题采纳率:94.7% 举报
(1))x 2 -7x-18=0,
(x-9)(x+2)=0,
x-9=0,x+2=0,
x 1 =9,x 2 =-2;
(2)
6 x 2 -x-2
6 =0 ,
b 2 -4ac=(-1) 2 -4×
6 ×(-2
6 )=49,
x=
1±
49
2
6 ,
x 1 =
2
3
6 ,x 2 =-
6
2 ;
(3)(2x-1)(x-3)=4,
整理得:2x 2 -7x-1=0,
b 2 -4ac=(-7) 2 -4×2×(-1)=57,
x=
7±
57
2×2 ,
x 1 =
7+
57
4 ,x 2 =
7-
57
4 ;
(4)(x+
2 ) 2 =4
2 x,
整理得:x 2 -2
2 x+2=0,
(x-
2 ) 2 =0,
x 1 =x 2 =
2 .
1年前
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