1) (a+z) (n-m) =a*n-a*m+z*n-z*m=an-am+zn+zm
2) (t+s) (b+r) =t*b+s*b+t*r+s*r=tb+sb+tr+sr
3) (c-d) (x-y) =c*x-c*y-d*x+d*y=cx-cy-dx+dy
4) (a+2) (b-3) =a*b+2*b-3*a-2*3=ab+2b-3a-6
5) (4-b) (5+c) =4*5-5*b+4*c-b*c=20-5b+4c-bc
6) (d-4) (t+5) =d*t-4*t+5*d-4*5=dt-4t+5d-20
7) (r-6) (7-b) =7*r-r*b-6*7+6*b=7r-rb-42+6b
1) (a+z) (n-m) =a*n-a*m+z*n-z*m=an-am+zn+zm
2) (t+s) (b+r) =t*b+s*b+t*r+s*r=tb+sb+tr+sr
3) (c-d) (x-y) =c*x-c*y-d*x+d*y=cx-cy-dx+dy
4) (a+2) (b-3) =a*b+2*b-3*a-2*3=ab+2b-3a-6
5) (4-b) (5+c) =4*5-5*b+4*c-b*c=20-5b+4c-bc
6) (d-4) (t+5) =d*t-4*t+5*d-4*5=dt-4t+5d-20
7) (r-6) (7-b) =7*r-r*b-6*7+6*b=7r-rb-42+6b