Question

Use the inequalitiy (x+1)(x-3)(x-7)(x+6)>0 what is the solution

Answer 1

Hello, to find the sign of the product we use the following rules.

- by + is -

"The enemy of my friend is an enemy."

+ by - is -

"The friend of my enemy is an enemy."

- by - is +

"The enemy of my enemy is a friend."

+ by + is +

"The friend of my friend is a friend."

We can build the following array.

`f(x)=(x+1)(x-3)(x-7)(x+6)`

So f(x) > 0 <=> x < -6 or -1 < x < 3 or x > 7

Thank you