I just started a proofs course in college and have been doing great so far with direct proofs (if x and y are both even, then x + y is even - simple stuff like that) ...until this last section hit us...I can't seem to do any of the proofs. We just learned what proof by contrapositive was. Here is one I have no idea about...
If ab > 0 and bc < 0, then ax^2 + bx + c =0 has two distinct real roots.
A couple issues arise...first, what is a distinct real root? She never mentioned it. I know real roots, but distinct...does that mean unique? or what?
Next, I cannot say whether or not a,b, or c is negative. All I know is one or more will have to be to fit both hypothesis.
If I should use proof by contrapositive, well..it simply leaves me stuck at the hypothesis ax^2 + bx + c = 0 does not have two distinct real roots. I still have no idea what to do with that knowledge or how to write it out to even get started with something...
2007-09-13
16:21:12
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2 answers
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asked by
Anonymous
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Mathematics