Resolución ejercicio 1

(a + b)(c + d) = (a + b)c + (a + b)d

(a + b)(c + d) = (ac + bc) + (ad + bd)

(a + b)(c + d) = [(ac + bc) + ad] + bd

(a + b)(c + d) = [ac + (bc + ad)] + bd

(a + b)(c + d) = [ac + (ad + bc)] + bd

(a + b)(c + d) = (ac + ad + bc) + bd

(a + b)(c + d) = ac + ad + bc + bd