Elementary Set Theory
posted by Matrix School 1 on .
An operation * is defined by the relation x*y = 5x + 3y  4xy
Evaluate (3*2)*4

well, 3*2= 15+624=3 check that
then 3*4 must be =15+12+48=45 check that. 
Everywhere you see the * symbol, use the function 5x + 3y  4xy, where x and y are the numbers to either side of the * symbol.
Order of operations still applies: start within the parentheses first.
3*2 = 5(3) + 3(2)  4(3)(2)
3*2 = 15 + 6  24
3*2 = 3
Now you have (3)*4
3*4 = 5(3) + 3(4)  4(3)(4)
3*4 = 15 + 12 + 48
3*4 = 45
So the answer is 45.