−6i is a root of f(x)=x3−20x2+36x−720. Find the other roots of f(x).Write your answer as a list of simplified values separated by commas, if there is more than one value.
Q. −6i is a root of f(x)=x3−20x2+36x−720. Find the other roots of f(x).Write your answer as a list of simplified values separated by commas, if there is more than one value.
Determine total number of roots: The number of roots is equal to the degree of the polynomial. We have:f(x)=x3−20x2+36x−720Determine the total number of roots. The degree of f(x) is 3. So, the number of roots: 3.
Find conjugate of −6i: If a+bi is a root, then its conjugate a−bi is also a root of f(x). Given root: −6i Find the conjugate of −6i. The conjugate is 6i. Since complex roots come in conjugate pairs for polynomials with real coefficients, 6i is also a root of f(x).
Divide by x2+36: Now we have two roots: −6i and 6i. We need to find the third root.Since the polynomial is cubic, we can use synthetic division or polynomial division to divide the polynomial by (x−(−6i))(x−6i)=(x+6i)(x−6i)=x2+36.Divide f(x) by x2+36 to find the quotient polynomial, which will be of degree 1.
Perform division: Perform the division:f(x)/(x2+36)=(x3−20x2+36x−720)/(x2+36)This division should give us a linear polynomial since we are dividing a cubic polynomial by a quadratic polynomial.
Division result: The division yields: x−20. This is because when we divide x3−20x2+36x−720 by x2+36, the x3 term is canceled by x×x2, the −20x2 term remains unchanged, and the 36x and −720 terms are canceled by −36×x and −36×20, respectively.
Find third root: The linear polynomial x−20 gives us the third root when set equal to zero:x−20=0Solving for x gives us the third root:x=20