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方程3x2+9=0的根为( ) A.3 B.-3 C.±3 D.无实数根
方程3x2+9=0的根为( )
A.3
B.-3
C.±3
D.无实数根
考点分析:
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下列方程中,适合用直接开方法解的个数有( )
①
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2=3;④x
2=x+3;⑤3x
2-3=x
2+1;⑥y
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2=x+3.
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B.2
C.3
D.4
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