bat dang thuc

K

kisihoangtoc

$(x-1)(x-3)(x-4)(x-6)+10$
$=(x^2-7x+12)(x^2-7x+6)+10$
$=(t+6)t+10$ Đặt $t=x^2-7x+6$
$=t^2+6t+10$
$=(t+3)^2+1$\geq$1$
 
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