LXY_2
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共回答了17个问题采纳率:82.4% 举报
(1)x 2 +6x-11=0,
x 2 +6x=11,
配方得:x 2 +6x+9=11+9,
(x+3) 2 =20,
开方得:x+3=±2
5 ,
x 1 =-3+2
5 ,x 2 =-3-2
5 ;
(2)2x 2 +6=7x,
2x 2 -7x=-6,
x 2 -
7
2 x=-3,
配方得:x 2 -
7
2 x+(
7
4 ) 2 =-3+(
7
4 ) 2 ,
(x-
7
4 ) 2 =
1
16 ,
开方得:x-
7
4 =±
1
4 ,
x 1 =2,x 2 =
3
2 ;
(3)x 2 -10x+25=7,
x 2 -10x=-18,
配方得:x 2 -10x+25=-18+25,
(x-5) 2 =7,
开方得:x-5=±
7 ,
x 1 =5+
7 ,x 2 =5-
7 ;
(4)3x 2 +8x-3=0,
3x 2 +8x=3,
x 2 +
8
3 x=1,
配方得:x 2 +
8
3 x+(
4
3 ) 2 =1+(
4
3 ) 2 ,
(x+
4
3 ) 2 =
25
9 ,
开方得:x+
4
3 =±
5
3 ,
x 1 =
1
3 ,x 2 =-3;
(5)(x-1)(x-2)=12,
x 2 -3x=10,
配方得:x 2 -3x+(
3
2 ) 2 =10+(
3
2 ) 2 ,
(x-
3
2 ) 2 =
49
4 ,
开方得:x-
3
2 =±
7
2 ,
x 1 =5,x 2 =-2.
1年前
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