Question

what happens to ax^2+bx+c, when b is change to -b? i understand that if a is -a then the parabola is facing down. how does -b effect it graphically?

Answer 1

It is shifted. If ax^2+bx+c can be broken down into the form (nx+r)^2, turning b into -b would cause it to become (nx-r)^2. Which means the zeroes are moved.

Answer 2

how does that look graphically? can you give me an idea?

Answer 3

How about you just use WolframAlpha to actually SEE an example? http://www.wolframalpha.com/