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# A few quick C1 questions... watch

1. (Original post by mik1a)
firstly, b^2-4ac > 0 for two distinct roots.
second, you shouldn't assume it is true and follow through by manipulating an equation. as a proof, you should take b^2-4ac, substitute in, rearrange it and show that it is positive irregardless of k. writing it as an equation leads you to do things like multiply by -1, which is silly because now you have 4ac-b^2, not what you want.

I do agree that the question looks like it was writen wrongly.
see above post. I misread the question.
2. (Original post by mik1a)
firstly, b^2-4ac > 0 for two distinct roots.
second, you shouldn't assume it is true and follow through by manipulating an equation. as a proof, you should take b^2-4ac, substitute in, rearrange it and show that it is positive irregardless of k. writing it as an equation leads you to do things like multiply by -1, which is silly because now you have 4ac-b^2, not what you want.

I do agree that the question looks like it was writen wrongly.
Even if he did prove b^2 -4ac > 0 for all values of k, but ..with k = 0. there's only 1 root, not 2 distinct roots. Hmm, u guys too mechanical,
3. (Original post by Widowmaker)
see the k^2.
hehe yes I know, but you said always use a graph for inequalities, just wires crossed then

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