Find a degree 3 polynomial with real coefficients having zeros 3 and 4 i and a lead coefficient of 1. Write P in expanded form. Be sure to write the full equation, including P ( x ) = .

Respuesta :

Answer:

[tex]P(x)=x^3-3x^2+16x-48[/tex]

Step-by-step explanation:

Given information:

  • Polynomial function with real coefficients.
  • Zeros: 3 and 4i
  • Lead coefficient of 1.

For any complex number  [tex]z=a+bi[/tex], the complex conjugate of the number is defined as  [tex]z^*=a-bi[/tex].  

If f(z) is a polynomial with real coefficients, and z₁ is a root of f(z)=0, then its complex conjugate z₁* is also a root of f(z)=0.

Therefore, if P(x) is a polynomial with real coefficients, and 4i is a root of f(x)=0, then its complex conjugate -4i is also a root of P(x)=0.

Therefore, the polynomial in factored form is:

[tex]P(x)=1(x-3)(x-4i)(x-(-4i))[/tex]

[tex]P(x)=(x-3)(x-4i)(x+4i)[/tex]

Expand the polynomial:

[tex]P(x)=(x-3)(x^2+4ix-4ix-16i^2)[/tex]

[tex]P(x)=(x-3)(x^2-16(-1))[/tex]

[tex]P(x)=(x-3)(x^2+16)[/tex]

[tex]P(x)=x^3+16x-3x^2-48[/tex]

[tex]P(x)=x^3-3x^2+16x-48[/tex]