SOLUTION: SQRT(x + 8) + SQRT(x + 15) = SQRT(9x + 40). This must be squared twice and I'm stuck.

Where are you stuck? Why don't you show what you've done so someone can see and tell you why and/or

where you're getting stuck? I got 

SOLUTION BELOW:


 ------ Squaring both sides

 









 ------- Squaring both sides













(x – 1)(45x + 191) = 0

		OR 		x =  (ignore)