2021/061) Prove that the number 9999999+1999000 is composite.

Let x = 1000 to keep it simple

So we get

$9999999+1999000  = 10^7-1 + 1999 * 1000$

$= 10 * 10^ 6 - 1+ (2000-1)* 1000$

$= 10 x^2 - 1 + (2x-1) x$ putting 1000 = x

$=12x^2 - x - 1$

$= (4x+1)(3x-1)$

$= 4001 * 2999$ putting back x = 1000 

Hence it is composite