Quang Truong

Ta có: $f(5)-f(4)=2012\Leftrightarrow 11a+9b+c=2012$

$f(7)-f(2)=335a+45b+5c=280a+(55a+45b+5c)=(280a+10060)\vdots 10$

Vậy $f(7)-f(2)$ là hợp số

sai roi kia: f(5) - f(4) = 61a + 9b + c = 2012

f(7) - f(2) = 335a + 45b + 5c = 5(61a + 9b +c) + 30a = 5.2012 + 30a= 10060 + 30a (la hop so vi a la so nguyen duong)

y tuong cua ban la dung nhung cach lam cua ban thi sai do ban da tinh nham