Urgent, 2009 Beijing senior high school entrance examination mathematics 25 questions (3) Question solving, when is the shortest? Why (must answer)?

I didn't count the first two questions. I don't know what a straight line is, so I can only say it roughly. Point P coordinates (0, a) and G coordinates (0, b).

The speed of y axis is 2, the speed of GA is 1, and a is a constant.

When P is higher than G, time =(a-b)/2+ root sign (a*a+6*6), and when this time is a=b, the value of this formula is the smallest, which means that P coincides with G, and when P is lower than G, (b-a)/2+ root sign (B * B+6 *).

Why can't junior high school students learn math well? These are all reasons.

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