Question 751034
solve x - 2 sqrt(x) = 35
x-2√x=35
let u=√x
u^2=x
u^2-2x-35=0
(u-7)(u+5)=0
u=7=√x
x=49
check:49-2√49=49-14=35
..
u=-5=√x
x=25
check:25-2√25=25-10=15 (extraneous root)