Math change in percentage question

Hi!
The answer for this question is A, i can’t find the right answer
Thank you for your help!

Hello Juliette! Let’s apply all the changes to the equation:

A = (1,5x + 1,5y)² . 0,8z . Q / 2P

A = (2,25x² + 2.2,25xy + 2,25y²) . 0,8z . Q / 2P

Now you can highlight 2,25 (and you’ll see that will be the total change in (x + y)²

A = 2,25 (x² + 2xy + y²) . 0,8z. Q / 2P

Let’s simplify it by putting all the numbers together after dividing 0,8 by 2.

A = 2,25 . 0,4 (x + y)² . z . Q / P

A = 0,9 (x + y)² . z . Q / P

As you can see, the original equation is being multiplied by 0,9, which means that A had a decrease of 10%

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Thank you for your help!

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