Can I square sqrt 37-11x = 9-x by first squaring the 9 and then the x? Like this (sqrt37-11x)^2=9^2-x^2 which one is correct? And why?

Question

 
sqrt37-11x = 9-x Can I square 9 minus x by first squaring the 9 then squaring the x? In other words, would this be correct: (sqrt37-11x)^2 = 9^2-x^2 Why or why not? If it is incorrect, what would be the correct way? 

Answer 1

The square of 9 - x IS NOT 9² - x².  The correct way to do it is:

 

(9 - x)² = (9 - x)(9 - x) = 9² - 9x - x(9) + (-x)² = 81 - 18x + x²