... x1 x2 = m + 2 2 AB2 = ( x1 x2 ) + 4( x1 x2 ) = ( x1 + x2 ) 4x1 x2 = m2 - 8m - 20 = m = 10 , m = - ( Tha (2) ) KL: m = 10, m = - 0 ,25 0 ,25 0 ,25 0 ,25 II-1 (1 im) II -2 (1 im) PT cos2x + ... 4log2 x 2log x iu kin: x> ; BPT 2 + x 20 VI.a -2 (1 im) t t = log x Khi ú x = 2 BPT tr thnh 42 t + 22 t 20 t y = 22 t ; y BPT tr thnh y2 + y - 20 - y i chiu iu kin ta cú : 22 t 2t ... x 2 0 ,25 0 ,25 A I H B 0 ,25 0 ,25 0 ,25 0 ,25 0 ,25 0 ,25 0 ,25 0 ,25 t VII.a (1 im) 0 ,25 0 ,25 0 ,25 10 x - y - = Ta im A l nghim ca HPT: A(3; 1) x + y - = VI.b- (1 im) VI.b -2 (1 im) 0 ,25 Gi B(b;...