Also (as an addition to the @MathTutor's solution) if the base
x^2 - 7x + 7 = 1,
then any degree of the base is 1.
x^2 - 7x + 7 = 1 ====> x^2 -7x + 6 = 0 ====> (x-6)*(x-1) = 0 ====> the roots are x= 6 and x= 1.
So, add these values x= 6 and x= 1 to the list of solutions.