Question

chứng minh rằng (10a+10b-a-b)chia hết cho9

Answer 1

=10a-a+10b-b

=9a+9b

=>nó chia hết cho 9

Answer 2

\(\text{Ta có : 10a + 10b - a - b = 10a - a + 10b - b }\)

\(=9a+9b=9\left(a+b\right)\)

\(\text{Vì }9\left(a+b\right)⋮9\Rightarrow\left(10a+10b-a-b\right)⋮9\)

Hk tốt