Which of the following expresses the possible number of positive real solutions for the polynomial equation shown below? x^3-4x^2-7x+28=0 a. two or zero b. two c. one d. two or one

Thru synthetic division I was able to show that 4 is a root of the given cubic equation, and that the coefficients of the quotient are {1, 0, -7}, which results in the polynomial x^2 - 7.  This poly. can be factored:

x = plus or minus sqrt(7).  We are interested ONLY in positive real solutions, of which there are exactly two:  { 4, +sqrt(7) }.