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-6i is a root of 
f(x)=x^(3)-20x^(2)+ 
36 x-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.

6i -6 i is a root of f(x)=x320x2+ f(x)=x^{3}-20 x^{2}+ 36x720 36 x-720 . Find the other roots of f(x) f(x) .\newlineWrite your answer as a list of simplified values separated by commas, if there is more than one value.

Full solution

Q. 6i -6 i is a root of f(x)=x320x2+ f(x)=x^{3}-20 x^{2}+ 36x720 36 x-720 . Find the other roots of f(x) f(x) .\newlineWrite your answer as a list of simplified values separated by commas, if there is more than one value.
  1. Determine total number of roots: The number of roots is equal to the degree of the polynomial. We have:\newlinef(x)=x320x2+36x720f(x) = x^3 - 20x^2 + 36x - 720\newlineDetermine the total number of roots. The degree of f(x)f(x) is 33. So, the number of roots: 33.
  2. Find conjugate of 6i-6i: If a+bia + bi is a root, then its conjugate abia - bi is also a root of f(x)f(x). Given root: 6i-6i Find the conjugate of 6i-6i. The conjugate is 6i6i. Since complex roots come in conjugate pairs for polynomials with real coefficients, 6i6i is also a root of f(x)f(x).
  3. Divide by x2+36x^2 + 36: Now we have two roots: 6i-6i and 6i6i. We need to find the third root.\newlineSince the polynomial is cubic, we can use synthetic division or polynomial division to divide the polynomial by (x(6i))(x6i)=(x+6i)(x6i)=x2+36(x - (-6i))(x - 6i) = (x + 6i)(x - 6i) = x^2 + 36.\newlineDivide f(x)f(x) by x2+36x^2 + 36 to find the quotient polynomial, which will be of degree 11.
  4. Perform division: Perform the division:\newlinef(x)/(x2+36)=(x320x2+36x720)/(x2+36)f(x) / (x^2 + 36) = (x^3 - 20x^2 + 36x - 720) / (x^2 + 36)\newlineThis division should give us a linear polynomial since we are dividing a cubic polynomial by a quadratic polynomial.
  5. Division result: The division yields: x20x - 20. This is because when we divide x320x2+36x720x^3 - 20x^2 + 36x - 720 by x2+36x^2 + 36, the x3x^3 term is canceled by x×x2x \times x^2, the 20x2-20x^2 term remains unchanged, and the 36x36x and 720-720 terms are canceled by 36×x-36 \times x and 36×20-36 \times 20, respectively.
  6. Find third root: The linear polynomial x20x - 20 gives us the third root when set equal to zero:\newlinex20=0x - 20 = 0\newlineSolving for xx gives us the third root:\newlinex=20x = 20

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