f(x)=x²−4x−21
The degree is the biggest power of x. That's a polynomial of degree 2, also called a quadratic function. Let's find its zeros.
0 = x²−4x−21 = (x - 7)(x+3)
x=7 or x=-3
The fundamental theorem guarantees every non-constant polynomial with complex coefficients has a complex zero, let's call it r. If we divide the polynomial by x-r there won't be any remainder and we'll get a new polynomial, one degree less. The fundamental theorem again applies and (if it's not a constant polynomial) we are assured of another zero, s. We divide by x-s and get a new polynomial of degree one less. We repeat all this until we get a constant polynomial (degree zero). So we get a zero for every degree. They're not necessarily all different.
Answer:
The degree of f(x) is 2. The Fundamental Theorem of Algebra guarantees that a polynomial equation has the same number of complex roots as its degree. This means that f(x) has exactly 2 zeros. Those zeros are 7 and -3.
