algebra
posted by jessica on .
(a minus sqrtx)^2=25
I have no idea of how to work this problem where i in up with the answers of a=7,3. Basiclly I just gave it a guess. Could someone show the steps I need to take. Thanks.

take the sqrt of each side.
asqrtx=+ 5
now work each possible sign
sqrtx=a5 or sqrt x=a+5
then square each side:
x=(a5)^2 or x=(a+5)^2
Now you are presented with a quandry, resolve this way. If the domain of x is restricted to real numbers, then you cant take a sqrt of a negative numer, so
x>= 0 which means
(a5)>0 or a>5 and (a+5)>0 a>5 but the first predominates, so a>5 is the restriction on a. 
what happen the the results of a=7, 3 to this problem because when I plug them in it equal to 25 in the end. Could you explain this a little more for me. Thanks.