-8+4x=-20x-25+7x
4x+20x-7x=-25+8
17x=-17 /17
x=-1
For a given degree of the polynomial, the number of turning points is given by n-1, where n is the degree of the polynomial. A polynomial that has x number of zeros is a polynomial of degree x. Thus the polynomial that has 9 zeros and 4 turning points, is a polynomial of degree 9.
For this specific equation the answer is x - 2