14-240/Classnotes for Monday September 8

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We went over "What is this class about?" (PDF, HTML), then over "About This Class", and then over the first few properties of real numbers that we will care about.

Dror's notes above / Students' notes below






The real numbers a set R with 2 binary operations +, *

+:R*RR

*:R*RR

in addition 2 special element 0,1∈ R s.t. 0≠1 & furthermore:

R1: The commutative law (for both addition and multiplication)

For every a,b∈R, we have a+b=b+a & ab=ba

R2: The associative law

For every a,b,c∈R, we have (a+b)+c=a+(b+c) (ab)c=a(bc)

in our lives pretty little girls (PL)G≠P(LG)


R3: a+0=a & a*1=a