Question

prove that AunionB union C =A union BunionC​

Answer 1

This can be proven by using associative law but for 4 marker you must prove like

let x be element of Aunion(BunionC)

x is element of A or BUC

so x is element of AUB and AUC

SO X IS ELEMENT OF AT LEAST 1 SET OF A B OR C

SO X IS ELEMENT OF (AUB)UC ........U ALSO NEED TO PROVE IT From OTHER SIDE

Y is Element of (AUB)UC

Y IS ELEMENT OF AUB AND C

Y IS ELEMENTBOF AT LEAST ONE OF THE SETS A B AND C

SO Y IS AN ELEMENT OF AU(BUC)

THESE STATEMENTS ARE TRUE 4 EVERY ELEMENT OF BOTH SETS SO ALL ELEMENT OF BOTH SETS ARE SAME ...SO BOTH SETS ARE EQUAL.

Answer 2

sorry I am unable to understand