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Unformatted text preview: 3. Fix real numbers a , b , c , and d . Prove that ( a + b ) + ( c + d ) = (( d + c ) + a ) + b. 2 MATH 74 MIDTERM 1 Instructions for 46. For the remaining three proofs you may make free use of the basic notational conventions of arithmetic (order of operations, no need for various parentheses, etc). As a general guide, anything above the numbered list of Facts on the handout, or anything that is one or two steps removed from those, may be assumed and used without explicit reference. If you use a listed fact, however, I would like you to cite it explicitly (in words, or by number). 4. Prove that for any n N , we have n j =1 j 3 = n 2 ( n +1) 2 4 . 5. Suppose that x is a rational number and that y is an irrational number. Prove that x + y is irrational. 6. Prove that for any n N , the number 5 2 n1 + 1 is an integer multiple of 6....
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This note was uploaded on 02/10/2010 for the course MATH 74 taught by Professor Courtney during the Fall '07 term at University of California, Berkeley.
 Fall '07
 COURTNEY
 Math

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