11.Prove that if a and b are rational numbers, b ≠ 0, and r is an irrational number, then a + br is irrational. (Hints: by contradiction)
12.Prove that for all integers m and n, if mn is even then m is even or n is even. (Hints: By contraposition)
Discrete Maths ..4..
2013-10-17 6:29 am
回答 (2)
2013-10-17 7:22 am
2013-10-17 7:18 am
11)
Suppose a + br = c is a rational number,
then r = (c - a)/b is a rational number since a , b , c are rational.(Contradiction)
Suppose a + br = c is a rational number,
then r = (c - a)/b is a rational number since a , b , c are rational.(Contradiction)
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