a) (a+b)(a-3)=a²-3a+ab-3b
b) (4-x)(x+z)=4x+4z-x²-xz
c)(m-12)(m-n)=m²-mn-12m+12n
d) (x-5)(x-y)=x²-xy-5x+5y
e) (6-u)(u+v)=6u+6v-u²-uv
f) (5-m)(m-n)=5m-5n-m²+mn
g) (x-3)(a-x)=ax-x²-3a+3x
h) (p+q)(p-1)=p²-p+pq-q
i) (s+t)(s-u)=s²-su+st-tu
j) (v-w)(u-w)=uv-vw-uw+w²