r2-2r1,r3-r1,r4-2r11 1 2 2 30 0 -4 a-4 -20 -1 a-2 -1 20 a-2 -1 1 -2r4+r3,r3+r21 1 2 2 30 0 -4 a-4 -20 -1 a-6 a-5 00 a-3 a-3 0 0r3+(a-3)r31 1 2 2 30 0 -4 a-4 -20 -1 a-6 a-5 00 0 (a-3)(a-5) (a-3)(a-5) 0...