As shown in the figure, point P is the point on the fixed length line AB, and points c and D respectively start from P and B and move to the left along the straight line AB at the speed of 1cm / s and 2cm / s As shown in the figure, P is the point on the fixed length line AB, and C and D respectively start from P and B and move to the left along the line AB at the speed of 1cm / s and 2cm / S (C is on the line AP and D is on the line BP) (1) If C and d move to any moment, there is always PD = 2Ac and ab = 6 Quick, quick,

As shown in the figure, point P is the point on the fixed length line AB, and points c and D respectively start from P and B and move to the left along the straight line AB at the speed of 1cm / s and 2cm / s As shown in the figure, P is the point on the fixed length line AB, and C and D respectively start from P and B and move to the left along the line AB at the speed of 1cm / s and 2cm / S (C is on the line AP and D is on the line BP) (1) If C and d move to any moment, there is always PD = 2Ac and ab = 6 Quick, quick,

It seems to be 2cm. First draw a picture and mark each point. Let PC = x and BD = 2x;
Similarly, since PD = 2Ac, let AC = y and PD = 2Y;
We also know that ab = 6, so the equation AB = AC + CP + PD + db; 6 = y + X + 2Y + 2x; X + y = 2
It can be seen from the figure that PA = AC + CP = x + y = 2
Let's see if we can