... f (2) m Khi ú gi s x1 =2; x2,x3 l nghim ca (2) Ta cú x2 + x3 = 2( 1 m), x2 x3 = m 0 ,25 2 Ta cú x + x + x = + (x + x ) 2x x = 4m 6m + 2 Câu 1,0 2 2 x 12 + x 22 + x 32 = 20 4m 6m + = 20 ... ta cú f (2 x) = f ( y 2) x = y Thay x = y 2( x 0) vo (2) c (2 x 1) x + = x3 52 x + 82 x 29 Câu 1,0 (2 x 1) x + = (2 x 1)(4 x 24 x + 29 ) (2 x 1) ( ) 0 ,25 x + x + 24 x 29 = x = ... cos x = 2( 3) +) (2) x = + k , x = + k 6 0 ,25 0 ,25 0 ,25 0 ,25 x = + k 12 sin x + ữ = x = + k 12 0 ,25 KL a)K: n Ơ , n 0 ,25 An2 3Cn2 = 15 5n n( n 1) Câu 1,0 3.n ! = 15 5n 2! (n ...