设交点为A(x1,y1),B(x2,y2)
x+b=x^2/2
x^2-2x-2b=0,△>0,b>-1/2
x1+x2=2,x1*x2=-2b
OA²+OB²=AB²
x1²+y1²+x2²+y2²=(x1-x2)²+(y1-y2)²
x1²+(x1+b)²+x2²+(x2+b)²=(x1-x2)²+(x1-x2)²
x1²+x1²+b²+2x1b+x2²+x2²+b²
+2x2b=2x1²+2x2²+2b(x1+x2)+2b²=2x1²+2x2²-4x1x2
2b(x1+x2)+2b²=-4x1x2
4b+2b²=8b
b=0或2
或高中的话可以用向量x1x2+y1y2=0
4b+2b²=8b
b=0或2