... x 2 ) = f(1, 0). x 2 + f(1, 1). x 2 Suy ra: f(x1, x 2 ) = f(0, 0) x1x 2 + f(0, 1) x1x 2 + f(1,0 )x1x 2 + f(1,1)x1x 2 Vỏỷy: 2 211 2 21x)x ,( 12 0ef ) ,( 21 ==xxftrong ... nhỏỳt theo 1 bióỳn (trong õoù xem mọỹt bióỳn laỡ hũng sọ ). Ta coù: f(x1, x 2 ) = f(0, x 2 ). x1 + f(1,x 2 ). x1maỡ: f(0, x 2 ) = f(0,0 ). x 2 + f(0, 1). x 2 vaỡ: f(1, x 2 ) = f(1, 0). ... f(x1, x 2 , x3 ) = f ( = 12 0e31, 2 , 3 ). x11. x 2 2 . x33f(x1, x 2 , x3 ) = f(0,0, 0) x1x 2 x3 + f(0,0, 1) x1x 2 x3 + f(0,1, 0) x1x 2 x3 + f(0,1, 1) x1 x 2 ...