Calculus chapter Inequalities

Question

hello can someone help me undersand the answers to Inequalities.

Inequalities
 1. 'When we pass from left to right through x= -7, x+7 changes sign,and therefore k(x)
becomes positive' Changes sign can you explain

Answer 1

1. tri tu under the werds av krats is beyond the smarts av einstein

2. him sae funkshun=0 at x=-7

Answer 2

There seem to be an answer. But no here.

Question what is pass from left to right. The answer is K(x). Is it K(x) or (x). How do you know it is positive?

It is more of a question than an answer