number properties

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number properties

by sud21 » Wed Jan 25, 2012 5:48 pm
x is a positive integer. If both the units' digit of (x+1)^2 and the units' digit of (x+3)^2 are 1, what is the units' digit of x-3?
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by rijul007 » Wed Jan 25, 2012 6:16 pm
sud21 wrote:x is a positive integer. If both the units' digit of (x+1)^2 and the units' digit of (x+3)^2 are 1, what is the units' digit of x-3?
those numbers which when squared give 1 as units digit are 1,9

let us say x+1 = 9
x+3 = 11
x = 8

x-3 = 5

Units digit for x-3 would be 5