Question

Help pls!!

Answer 1

Answer:

B) 5

Step-by-step explanation:

We are given the function:

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

We are given that f(a) = 40 and a > 0 and we want to determine the value of a.

Substitute:

$f(a)=40=a(a+3)$

Distribute:

$a^2+3a=40$

Subtract 40 from both sides:

$a^2+3a-40=0$

We can factor using 8 and -5. Hence:

$(a+8)(a-5)=0$

By the Zero Product Property:

$a+8=0\text{ or } a-5=0$

Solve for each case:

$\displaystyle a=-8\text{ or } a=5$

Since a > 0, we can eliminate the first solution. Hence:

$a=5$

Our answer is B.