Tính S = 2xA - 3xB

Cho ham so y=x^3 -3x +1 co do thi (C). Goi A( xA; yA), B( xB;yB ) voi xA > xB la cac diem thuoc (C) sao cho cac tiep tuyentai A,B song song voi nhau va AB =6 can (37). Tinh S= 2xA -3xB