Given those properties you need to convince yourself that
y'=0 when t=0 and when x=t
so y'=aconstant *y*(y-7) the constant can be any negative number.
Most people would choose -1 but I'll choose -5 just tto be different
y'=-5y(y-7)
Alan's answer is also correct.
When you mult out the coefficient of y2 must be negative and this will be true for Alan's answer as well as mine. 