(1)计算:2sin60°-13+(13)-1+(-1)2012(2)解方程:2x2-3x-1=0
(1)计算:2sin60°-13+(13)-1+(-1)2012(2)解方程:2x2-3x-1=0....
(1)计算:2sin60°-13+(13)-1+(-1)2012(2)解方程:2x2-3x-1=0.
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(1)2sin60°-
+(
)-1+(-1)2012
=2×
?
+3+1
=
+4;
(2)2x2-3x-1=0,
a=2,b=-3,c=-1,
b2-4ac=(-3)2-4×2×(-1)=17>0,
x=
,
x1=
,x2=
1 | ||
|
1 |
3 |
=2×
| ||
2 |
| ||
3 |
=
2
| ||
3 |
(2)2x2-3x-1=0,
a=2,b=-3,c=-1,
b2-4ac=(-3)2-4×2×(-1)=17>0,
x=
3±
| ||
4 |
x1=
3+
| ||
4 |
3?
|