This is actually a sample GRE problem: a quantitative comparison between sqrt(79*80*81*82) and 6400. I recognized that 6400 = sqrt(80*80*80*80) and was therefore faced with comparing 79*81*82 to 80*80*80. I got the right answer, but it was only a guess on my part. So if I didn't have a calculator handy, how could I know that 79*80*81*82 was greater than 80*80*80*80?
I know that it is NOT true, for an arbitrary integer x, that (x-1)x(x+1)(x+2) > x^4. (It doesn't, for example, work for 1, or -1, or -2, or 0.)
2007-12-29
12:39:41
·
3 answers
·
asked by
AxiomOfChoice
2
in
Mathematics