# Proof by induction

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Thread starter 1 year ago
#1
Prove x^3 + 3x^2 - 10x is a multiple of 3 for all positive integers. How do you even prove its divisible by 3 for n = k?
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1 year ago
#2
(Original post by bluebear25618)
Prove x^3 + 3x^2 - 10x is a multiple of 3 for all positive integers. How do you even prove its divisible by 3 for n = k?
Are you sure this is an induction proof? Deduction seems more appropriate..
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1 year ago
#3
(Original post by bluebear25618)
Prove x^3 + 3x^2 - 10x is a multiple of 3 for all positive integers. How do you even prove its divisible by 3 for n = k?
What have you been taught about proof by induction so far? What have you got so far?

For proof by induction, there's a set layout you can use every time, so if you know that, it should be quite easy.
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Thread starter 1 year ago
#4
Yeah it's a homework for proof by induction. Think I may have it now though so dont worry!
(Original post by dextrous63)
Are you sure this is an induction proof? Deduction seems more appropriate..
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