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用适当的方法解下列方程:(1)x2-2x-9=0;(2)(5x-3)2+2(3-5x)=0
2个回答
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(1)a=1,b=-2,c=-9,
△=b2-4ac=4+36=40>0,有两个不相等的实数根,
x=
=
=1±
,
x1=1+
,x2=1-
;
(2)原方程变形为:(5x-3)2-2(5x-3)=0,
(5x-3)(5x-3-2)=0,
5x-3=0,5x-5=0,
x1=
,x2=1.
△=b2-4ac=4+36=40>0,有两个不相等的实数根,
x=
?b±
| ||
2a |
2±
| ||
2 |
10 |
x1=1+
10 |
10 |
(2)原方程变形为:(5x-3)2-2(5x-3)=0,
(5x-3)(5x-3-2)=0,
5x-3=0,5x-5=0,
x1=
3 |
5 |
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