题目内容：

Math question谢谢了,
Hey,guys,I'm currently in survey of calculus 1.I have a question that I need help with.I know the answer is B,but I don't really get what they are asking,greater than 50,but decreasing?I need the steps in detail,please walk me through it.Thanks a lot!As a fish passes the nest of a rival fish,the percent probability P that it will be attacked is given by P(x)=42+10x-x^3 where x is its distance (in feet) from the nest.Of the choices below,at which distance x is the probability of attack greater than 50 percent,but decreasing.A.1ft B.2ft C.3ft D.4ft E.5ft

优质解答

(1).Given that P(x)=x^3-10x+8 then,f(x)=P'(x)=3x^2-10 when P'(x)