本刊1996年第1期第7页上有一道练习题:“当a>0,b<0时,函数y=ax~2+bx与函数y=ax+b的图象大概是 ( ) 因a>0,抛物线的开口方向向上,故(C)、(D)可排除,又因为b<0,作为直线的截距是负的,故(A)也应排除.所以只可选(B). 但(B)是否正确呢?因为当x=-(b/a)时,有y=ax~2+bx=0,y=ax+b=0,即函数y=ax~2+bx与y=ax+b在x轴上相交于 There is an exercise question on page 7 of the first issue of the 1996 issue: “When a>0 and b<0, the image of the function y=ax~2+bx and the function y=ax+b is probably (). a>0, the direction of the opening of the parabola is upward, so (C), (D) can be excluded, and because b<0, the intercept as a straight line is negative, so (A) should also be excluded. So only optional (B ). But is (B) correct? Because when x=-(b/a), there are y=ax~2+bx=0, y=ax+b=0, that is, the function y=ax~2+bx Intersecting y=ax+b on the x-axis