Question

multiply. use the pattern (a+b)(a-b)= a squared - b squared
102 * 98

Answer 1

@ParthKohli gave you answer to your previous question. This one is just the same.
\[(100+2)(100-2)=100^{2}-2^{2}\]

Answer 2

watching at the nummbers 102 and 98 you have to find two numbers a and b such that:
a+b=102 and a-b=98
later: (a+b)(a-b) will be same as write 102*98,
but \[(a+b)(a-b)=a ^{2}-b ^{2}\]
which is more easy to multiply. That's it