Question

Answer 1

Bài 3: 

a: \(\left(3n-1\right)^2-4\)

\(=\left(3n-1-2\right)\left(3n-1+2\right)\)

\(=3\left(n-1\right)\left(3n+1\right)⋮3\)

b: \(100-\left(7n+3\right)^2\)

\(=\left(10-7n-3\right)\left(10+7n+3\right)\)

\(=\left(7-7n\right)\left(7n+13\right)⋮7\)