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# Discrete Math Question. I'm not sure what I did wrong for this question. ?

Suppose that a and b are integers where a ≡ 4 (mod7) and b ≡ 6 (mod7). Find the integer c with 0 ≤ c ≤ 6 such that c ≡ 2a + 4b (mod7).

c =

I got 4 as my answer but the correct answer is 11. I'm not sure how you get that. Can someone please explain this?

### 2 Answers

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- ted sLv 71 month ago
11 = 4 ( mod 7)....& 11 is not in [ 0 , 6 ]....and it should be ( 2a + 4 b)(mod 7 )...and 2a = 1 (mod 7) , 4b = 3(mod 7 )...and the ' answers ' in texts are not always valid

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