A(-2，0)B(0，-2)

(2) Solution: After δδAOB rotates 90 counterclockwise around point O, point A' coincides with point B..

∴A、(0,-2)B'(2,0)

∴ substitute a, (0,-2) b' (2,0) into y = ax2+2ax+c.

Required: -2=C

0=4a+4a-2

Solution: A = 1/4

C=-2

∴y= 1/4X^2+ 1/2X-2

(3) Solution: ∫△bb' d∽△a? ′B′B

Point d is on the x axis.

∠∠B′DB =∠ABB '

∴D(0,0)