Question

试说明N=5的平方×3的2n+1次方×2的n次方－3的n次方－3的n次方×6的n＋2次方能被13整除

Answer 1

N=25*3^(2n+1)2^n-3^(2n+2)2^(n+2)
=3^(2n+1)2^n[25-3*2^2]
=13*3^(2n+1)2^n
所以消侍虚能被13整拿燃谈衫除

Answer 2

5^2×3^(2n+1)×2^n-3^n×6^(n+2)
=5^2×3^(2n+1)×2^n-3^n×(2×3)^(n+2)
=5^2×3^(2n+1)×2^n-3^n×2^(n+2)×3^(n+2)
=5^2×3^(2n+1)×2^n-3^(2n+2)×2^(n+2)
=5^2×3^(2n+1)×2^n-3^(2n+1)×3×2^n×2^2
=3^(2n+1)×2^n×[5^2-3×2^2]
=3^(2n+1)×2^n×[25-12]
=3^(2n+1)×2^n×13