Show that if a cb, then a = b ( b a ). show that if a c b, then a u (b \ a) = b. show, by example, that for sets a, b, and c, an b = an c does not imply b = c.

If A ⊂ B, then A = B \ ( B \ A)

ok, when you do B \ A, you are subtracting all the elements in A∩B from B. So the only elements remaining are those who aren't in A.

If we subtract this of B again, we are subtracting of B all the elements that aren't in A, so the only elements remaining are those who belongs in A.

If A ⊂ B then A U (B \ A) = B.

Again, when you do B \ A you are extracting all the elements that belongs to the A∩B from B. So you are extracting al the elements from A. and when you add all the elements of A again, then you recuperate B.

if AnC = AnC does not imply that B = C.

if A = {1,2}, B = {1,2,3,4,5} and C = {1,2,3}

then AnC = {1,2} and AnB = {1,2} but B and C are different.

the multiples of 15 are 15, 30,45, 60, 75, 90, 105, 120, 135, 150, 165, 180, 195,   210, 225, 240, 255, 270, 285, 300, 315, 330, 345, 360, 375,   390, 405, 420, 435, 450, 465, 480, 495, 510, 525, 540, 555, 570, 585, 600, 615, 630, 645, 660, 675, 690, 705, 720, and 735.

the factors of 15 are 1, 3, 5, and 15.

hope that , fam!

-une, your fren : )