Find the constant ccc such that the tangent to f(x)=xf(x) = \sqrt{x}f(x)=x at x=cx=cx=c passes through (0,−1)(0, -1)(0,−1).
c=1c = 1c=1
c=2c = 2c=2
c=4c = 4c=4
c=1/4c = 1/4c=1/4