What is the equation of the common tangent to y2=4xy^2 = 4xy2=4x and x2=4yx^2 = 4yx2=4y?
x+y+1=0x + y + 1 = 0x+y+1=0
x+y=0x + y = 0x+y=0
x+y+2=0x + y + 2 = 0x+y+2=0
x+y−1=0x + y - 1 = 0x+y−1=0