Answer:
( x + y )² = 32
Explanation:
So far, I can tell that your calculations are incorrect. ( x + y )² is indeed x² + 2xy + y², which you can prove right by expanding the expression ( x + y )( x + y ). You simply swapped the positioning in this second step, and decided that the addition of x² + y² is x²y², but that is incorrect. You can't combine the two terms unless you multiply the two.
We should just be left with the expanded expression x² + y² + 2xy. Given that x² + y² = 17, and xy = 7.5, let's substitute and solve for the value of the expression.
17 + 2( 7.5 ) = 17 + 15 = 32,
( x + y )² = 32