Algebra 1 Question- Graphing parabolas...

I don't understand it. As in, graphing equations like y=x^2 on a coordinate plane. Our book doesn't give a very good explanation and I'm afraid to ask my teacher since she taught it like three months ago, and I'd probably just get in extreme trouble for not asking sooner.

I assume you know how to calculate x^2. so, for a parabola, you simply caclulate the value of y for various values.

Example:

y=x^2

to graph it, find the value of y when x=0,1,2,3.-1,-2,-3. when x=0, y=0. when x is 1 or -1, y=1. when x=2 or -2, y=4. when x=3 or -3, y=9. Plot these points on your graph, and draw a curved line through them, continuing with the current pattern. the parbola continues getting steeper as the number increases in absolute value.

To expand upon that (because tables of values suck ), There are faster ways depending on your equation.

In vertex form ( y = a(x+h)squared + k )

-h is the x coordinate of your vertex and k is your y co-ordinate.

a is your vertical stretch, so it tells you whether the parabola opens up or down, and how stretched it is. If a is positive it opens up, and if negative it opens down.

If, for example, a was 3, you would move over 1 and up three on both sides of your vertex for two more points on your parabola, and from there it is just a matter of drawing it.

With factored form , for example, y = (x+5)(x+7), it gives you your roots (in this case -5 and -7).

Given the roots, you find your axis of symmetry, substitute it into your equation to solve for y, and thus, have your vertex. With three plotted points, you can draw the parabola.

From standard form (y = ax squared + bx + c ), it is easiest to either use partial factoring or convert it into vertex form by completing the square. (I can explain either of these upon request, but unless you say otherwise, I assume you have learned them).