pre calculus problem?

Question

I have the answers to the problems but I need to know how to work it out if anyone can help that would be great! Thanks.

Consider the polynomial (x-a) (x-b) and the real number line

a) identify the points on the line at which the polynomial is zero. (see figure)
b) In each of the three subintervals of the line, write the sign of each factor and the sign of the product.
c) for which x-values does the polynomial change signs?

figure:
---o-----------------------o----->
a b

o stands for a closed circle btw

Answer 1

If a and b positive and b>a, then
---0------a--------b-------- where 0 stands fo zero on x-axis.

If a<0 and b> 0, then:
-----a----0------b------

If both a and b <0, then:
-----a-------b------0---------

If x x or if xa then polynomial changes sign.

I do not understand what you mean by the 3 subintervals and the sign of the factors, and their products.

Answer 2

isn't it hard to post math questions on yahoo LOL, without drawing, how the "blank" you show integrals, LOL