I'm stumped on a Gr. 11 math lesson, and I can't find it on google. I didn't see any in GD, so would fast threads be the place to ask?
Awesome. I need to find the points of intersection of a parabola, and this is how the teacher taught us to answer these questions: [URL]http://imgur.com/a/1Fx5n[/URL]
Basically, you are given two y equations, you simplify them to get ax^2 + b^2 + c and you plug a,b,c into the formula near the center of the page (the one that looks like x = -b±(square root of b^2) and so on). Here is how the textbook teaches it: [URL]http://i.imgur.com/W135uXT.jpg?1[/URL]
Now, I can do the sample my teacher taught me in the first pic, but when I apply it to a homework question then I can't figure it out. 1. a) for example [URL]http://i.imgur.com/sr5JWGX.jpg[/URL] is supposed to be (4, 3), (5,5) for the points of intersection, but I can't even get whole numbers for the coordinates. I think my problem is that I don't simplify the equation correctly for the a,b,c values, because I end up getting negative values to be square rooted (which gives me an error/undefined).
For 1.a), this is how I simplify it: [URL]http://i.imgur.com/s6eSe0T.jpg[/URL]
Where did I go wrong? I apologize if I grossly misunderstood the way she did the equation, I've been out of school for two years and I struggle.
[QUOTE=Trebgarta;51248932]
Look, the theory is, on these two points the x and y values of the two systems are equal. So if you can simplify the two equations to y = expression, those two different expressions would be equal to each other because y's are equal. So:
2x-5 = x2-7x+15
0 = x2 - 7x -2x +15 +5
0 = x2 -9x +20
[/quote]
Oh alright, so the 2x is negative because it had to be subtracted to be brought to the other side?
Vice versa with 5?
Why do we put 0 = whatever instead of y = whatever ?
Awesome, that makes sense. And I got the right answer! You've helped a bunch, thank you so much :)
There's a Mathematics thread in GD:
[url]https://facepunch.com/showthread.php?t=1428523[/url]
Your question has been answered so I am closing this thread.
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