Write out careful proofs, or give counterexamples, to the following statements. (a) Show that the sum of the squares of any three consecutive integers, plus one, is divisible by 3.

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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Write out careful proofs, or give
counterexamples, to the following statements.
(a) Show that the sum of the squares of any three consecutive integers, plus
one, is divisible by 3.
(b) Show that the sum of any four consecutive integers is divisible by 4.
(c) A function ƒ: A → B has an inverse if and only if it is both surjective
and injective.
(d) If f is not surjective, then it is injective.
(e) If g is surjective, then fog is surjective.
(f) If g and fog are injective, then 9 is injective.
(g) If ƒ og: R → R is decreasing, and g: R → R is decreasing, then f is
decreasing.
(h) If x = R and x² < x, then x < 1.
Transcribed Image Text:Write out careful proofs, or give counterexamples, to the following statements. (a) Show that the sum of the squares of any three consecutive integers, plus one, is divisible by 3. (b) Show that the sum of any four consecutive integers is divisible by 4. (c) A function ƒ: A → B has an inverse if and only if it is both surjective and injective. (d) If f is not surjective, then it is injective. (e) If g is surjective, then fog is surjective. (f) If g and fog are injective, then 9 is injective. (g) If ƒ og: R → R is decreasing, and g: R → R is decreasing, then f is decreasing. (h) If x = R and x² < x, then x < 1.
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