Question

For which values of z in the function f(z) positive? F(z) = (z-7)(z+5)

Answer 1

Given:

`f(z)=(z-7)(z+5)`

Multiply of two number is positive that mean both number is positive or both number is negative so:

For both positive :

`z>7`

For both negative :

`z<-5`

For function is positive

`\begin{gathered} (-\infty,-5)\cup(7,\infty) \\ or \\ -5>z>7 \end{gathered}`

(B)

for function negative:

One factor is positive and another factor is negative:

[tex]-5