Cao đẳng - Đại học
... x2+3x 3 =3, 3x1+ x2− 5x 3 =0,4x1− x2+ x4 =3, x1+3x2− 13x 3 = −6.(DS. x1=1,x2=2,x 3 =1)27.2x1− x2+ x 3 − x4=1,2x1− x2− 3x4=2,3x1− x 3 + ... tr`ınh1)x1+2x2+3x 3 =6,2x1− x2+ x 3 =2,3x1− x2− 2x 3 =2.(4.7)2)x1− 2x2+3x 3 − x4=6,2x1+3x2− 4x 3 +4x4=7,3x1+ x2− 2x 3 − 2x4=9,x1− 3x2+7x 3 +6x4= −7.(4.8)Gia’i. ... x1=1,x2=2,x 3 = −2)29.2x1+3x2+4x 3 +3x4=0,4x1+6x2+9x 3 +8x4= 3, 6x1+9x2+9x 3 +4x4=8.(DS. x1=72−3x22, x 3 = −1, x4= −1, x2t`uy ´y) 30 .3x1+3x2− 6x 3 −...