Question

Which of the following are roots of the polynomial function? Check all that apply. F(x) = x3 - 5x2 - 13x - 7

Answer 1

Write properties of function:

x intercept/zero:
`x_(1) =-1;x_(2) =7`

Explanation:

x² - 6x - 7 = x² - 7x + x - 7

⇒ x(x - 7) + 1(x - 7)

⇒ (x + 1) (x - 7)

Thus, x³ - 5x² - 13x - 7 = (x + 1)(x + 1)(x - 7)

Answer 2

`~~~~~~~~x^3 -5x^2 -13x -7=0\\\\\implies x^3 +x^2 -6x^2 -6x-7x-7=0\\\\\implies x^2(x+1) -6x(x+1) -7(x+1)=0\\\\\implies (x+1)(x^2 -6x -7) = 0\\\\\implies (x+1)(x^2 +x -7x-7)=0\\\\\implies (x+1) [x(x+1) -7(x+1)]=0\\\\\implies (x+1)(x+1)(x-7) = 0\\\\\implies (x+1)^2 (x-7) = 0\\\\\implies x = -1,~ x = 7\\\\\text{Hence, the roots are}~ -1~ \text{and}~ 7`