(A + B)(A + C)
= AA + AC + BA + BC
= A + AC + BA + BC
= (A + AC) + BA + BC
= A(1 + C) + BA + BC
= A + BA + BC
= (A + BA) + BC
= A + BC
证毕
(A + B)(A + C)
= AA + AC + BA + BC
= A + AC + BA + BC
= (A + AC) + BA + BC
= A(1 + C) + BA + BC
= A + BA + BC
= (A + BA) + BC
= A + BC
证毕