|May 21st, 2014, 02:25 AM||#1|
Joined: Apr 2013
Axis of Symmetry
I have to sketch a parabola y=-0,01x^2 -2x
I can calculate or know this things: parabola opens downward, graph is flat, graph goes through the origin, one of its intercepts is the origin.
y intercept (0,0) x1 intercept (-200,0) x2 intercept (0,0) Vertex (-100,100)
However I have now idea in which way I can "calculate" the coordinate (50,-125) (with the concept "axis of symmetry").
|May 21st, 2014, 01:10 PM||#2|
Joined: May 2014
It is difficult to understand your description. You may need to try and explain in a simpler way and give more details.
In case it helps, I have made some videos on basic concepts of high school maths.
|May 22nd, 2014, 01:48 AM||#3|
Joined: Nov 2013
Math Focus: Geometry
$\displaystyle y=-0,01x^2 -2x $
x & y \\ \hline
0 & 0 \\ \hline
-200 & 0 \\ \hline
-100 & 100 \\ \hline
put numbers for x and find y, then xonnect points of (x,y)
|May 22nd, 2014, 03:01 AM||#4|
Joined: Apr 2014
Math Focus: Physics, mathematical modelling, numerical and computational solutions
The intercepts and the vertex are all the information you need to sketch the quadratic. So you're done already!
The axis of symmetry is just a vertical line of symmetry that runs through the vertex.
The coordinate (50, -125) is an arbitrary coordinate that has nothing to do with the axis of symmetry. If you know that x = 50, substitute it in to get the y-coordinate. If you know the y-coordinate, set y equal to it and solve for x. You'll get two answers, so one of them will be (50,-125) and the other will be (-250,-125). You can just solve the quadratic with y = -125 or you can try the following:
If you already know one solution, you can get the other if you know the x-coordinate of the vertex. Let's say I know (50,-125) is a coordinate on the curve and I want the other point (a,-125). I find the horizontal distance between the coordinate I know (50) and the vertex (-100). This distance (150) is then transferred over to the other side of the vertex (-100 - 150 = -250). Therefore, the other coordinate is (-250,-125).
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