Analysis: (3) When a 1O 1∨y axis can be obtained, b 1 o/∨ x axis can be obtained, and then points o 1 and b/kl can be obtained. ② When points A 1 and B 1 are on parabola, the abscissa of point B 1 is displayed, and then the equation can be solved according to the length of the difference between the ordinate of two points A 1O 1.

Answer: (3)∫△AOB rotates 90 counterclockwise around point M,

∴A 1O 1∥y axis, b 1o 1∑x axis, and the abscissa of point A 1 is x,

① when points O 1 and B 1 are on parabola, the abscissa of point O 1 is x, and the abscissa of point B 1 is x+ 1.

∴ 1/2x^2-5/4x- 1= 1/2(x+ 1)^2-5/4(x+ 1)- 1，

X=3/4，

② when points A 1 and B 1 are on parabola, the abscissa of point B 1 is x+ 1, and the ordinate of point A 1 is 4/3 larger than that of point B 1.

∴ 1/2x^2-5/4x- 1= 1/2(x+ 1)^2-5/4(x+ 1)- 1+4/3，

X=-7/ 12，

To sum up, the abscissa of point A 1 is 3/4 or -7/ 12.

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