walker wrote:
automan wrote:
From S1 we know that a·x^2+b=-a·x^2+d => x= +/- sqrt[(d-b)/(2·a)]
We can not conclude anything because if b=d then the two paraboles cross in just one point so they do not really cross each other.
From S2 we can not conclude anything
From S1 & S2 we know that b and d are different and that x= +/- sqrt[(d-b)/(2·a)] , which means two different points, so they cross.
Answer should be C.
(d-b)0: (d-b)/(2·a) √((d-b)/(2·a)) is undefined. There are no roots.
a0 ==> √((d-b)/(2·a)) is defined. There are two roots.
Insuff.
Humm...tricky question. I think you are right. I got a bit confused not considering the sign of a. I considered a being either positive or negative. In such a case you can conclude that the paraboles either cross or not cross. You are right, E should be the answer.
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