2.49 1) х+у+z= 2a2-3ab-b2+a2+2ab+b2+4a2+2ab=7a2+ab
2) x-y-z=2a2-3ab-b2-a2-2ab-b2-4a2-2ab=5a2-7ab-2b2
3) -x-y+z=-2a2+3ab+b2-a2-2ab-b2+4a2+2ab=a2+3ab2b2
2/50 1) a2(a+2)-(3a+5)
2) 2(2x4+a3-2)+5a2
2.51 1) A=8x2+7xy-y2-6x2+3xy=2x2+10xy-y2
2) A= 4an+5bm+c+8an-2bm+c=12an+3bm+2c
3) A=3xn+1+10xn-7x-5