抛物线y=2x^2即x^2=1/2x 2p=1/2 p=1/4
焦点坐标(1/8,0)准线方程x=-1/8
y'=4x 抛物线在A处的切线的斜率=4
抛物线在A处的切线方程是y-2=4(x-1)
即4x-y-2=0