Question

Which of the following statements is true concerning f(x)=x^2-2x-15? Choose one. A) the zeros of f(x) are 3 and -5 since f(x)= (x+3)(x-5)B) the zeros of f(x) are 3 and -5 since f(x)= (x-3)(x+5)C) the zeros of f(x) are -3 and 5 since f(x)= (x+3)(x-5)D) the zeros of f(x) are -3 and 5 since f(x)= (x-3)(x+5)

Answer 1

To be able to solve this question, we must first factorize the quadratic expression first.

$\begin{gathered} f(x)=x^2-2x-15 \\ =x^2-5x+3x-15 \\ =x(x-5)+3(x-5) \\ =(x+3)(x_{}-5) \\ \\ x+3=0 \\ x=-3 \\ \\ x-5=0 \\ x=5 \end{gathered}$

From the above calculations, we can tell that the zeros of the expression which are also the solution to the expression are -3 and 5.

So the correct answer is C.