need help with this problem

[Guest]

given that a*b=(a+b)-ab, a and b are real numbers

Prove: a*(b*c)=(a*b)*c is true

 

[dtoepel]

You may have written this wrong. The result you are trying to prove is jusr the standard associative property of multiplication. Check the orginal problem and repost if necessary.
Dave

 

[stapel]

Given that a*b=(a+b)-ab, where a and b are real numbers, prove that a*(b*c)=(a*b)*c

Just evaluate according to the formula for the * ("star") operator, and compare what you get:

. . . . .b*c = b + c - bc

. . . . .a*(b*c) = a + [b + c - bc) - a[b + c - bc]

. . . . .= a + b + c - bc - ab - ac + abc

Now you do the right-hand side of the equation, and see what you get.

Eliz.

 

[Guest]

Thanks again
it came out exactly the same as the one you did.