Question 438756
sqrt(x)+sqrt(x-7)=21/sqrt(x-7
..
sqrt(x)+sqrt(x-7)=21/sqrt(x-7)
LCD: sqrt(x-7)
sqrt(x^2-7x)+x-7=21
sqrt(x^2-7x)=28-x
square both sides
x^2-7x=28^2-56x+x^2
49x=28^2=784
x=784/49
x=16 (ans)