Question

CMR  3a+4b chia hết cho 11 thì a+5b cũng chia hết cho 11 

Answer 1

Ta có:

\(\left(3a+4b\right)⋮11\)

\(\Rightarrow4\left(3a+4b\right)⋮11\)

\(\Rightarrow\left(12a+16b\right)⋮11\)

\(\Rightarrow\left(\left(11a+11b\right)+\left(a+5b\right)\right)⋮11\)

\(\Rightarrow\left(a+5b\right)⋮11\)

Answer 2

3a+4b chia hết cho 11

=>12a+16b chia hết cho 11

(12a+16b) - (a+5b) = 11a+11b

11a+11b chia hết cho 11

12a+16b chia hết cho 11

=>a+5b chia hết cho 11