1) (a+b)(x - y) 2)(a-b)(x+y) 3)(m-n)(p+q) 4)(a+b)(a+2)
1)(a+b)(x-y)=ax-ay+bx-by 2)(a-b)(x+y)=ax+ay-bx-by 3)(m-n)(p+q)=mp+mq-np-nq 4)(a+b)(a+2)=a²+2a+ba+2b