二次函数y=ax2+bx+1(a≠0)的图象的顶点在第一象限,且过点(-1,0).设t=a+b+1,则t值的变化范围是( )
A. 0<t<1
B. 0<t<2
C. 1<t<2
D. -1<t<1
人气:218 ℃ 时间:2019-08-22 12:21:02
解答
∵二次函数y=ax2+bx+1的顶点在第一象限,且经过点(-1,0),∴易得:a-b+1=0,a<0,b>0,由a=b-1<0得到b<1,结合上面b>0,所以0<b<1①,由b=a+1>0得到a>-1,结合上面a<0,所以-1<a<0②,∴由①+②得:-...
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