Question

#13, can you please teach me how to do this, have not been taught this.

Answer 1

Given:

$f(x)=(x-3)(x+8)$

Express the function in the following form,

$f(x)=a\text{x}^2+bx+c$

It becomes,

$\begin{gathered} f(x)=(x-3)(x+8) \\ f(x)=x(x+8)-3(x+8) \\ f(x)=x^2+8x-3x-24 \\ f(x)=x^2+5x-24 \\ \text{Compare it with f(x)=ax}^2+bx+c\text{ it gives,} \\ a=1,b=5,c=-24 \end{gathered}$

Answer:

$\begin{gathered} f(x)=x^2+5x-24 \\ a=1,b=5,c=-24 \end{gathered}$