For what value of ccc is the line y=x+cy = x + cy=x+c tangent to the parabola y=x2+2xy = x^2 + 2xy=x2+2x?
c=−12c = -\frac{1}{2}c=−21
c=−14c = -\frac{1}{4}c=−41
c=0c = 0c=0
c=14c = \frac{1}{4}c=41