SAT Official Question of the Day for 11/18, but do it MY WAY!
Try one. How about -8? So, we assume b = -8. Press ‘Y=’ on your TI-84 Plus (top left). Type into Y1: -2x^2-8x+5. That’s the function you get if you substitute -8 for b. Now press GRAPH (top right). (Do ‘ZOOM-6’ if you need a better picture.) What is the x-value of the highest point? It looks like about -2. The question says it should be 2. So, it’s not choice (a).
Try the next one: -4. Change Y1 (just type 4 over the 8), and press GRAPH again. This time it looks like the highest point is at x=-1. Still not right. It’s not choice (b).
Try 8. Change Y1 (just type +8 over the -4), and press GRAPH again. This time it looks like the highest point is at x=2. Choice (d) is correct.
And *THIS* is why I tell all of you to get the TI-84 Plus Graphing Calculator! Get one now: http://amzn.to/1tXyOTH