Equations containing radicals

[joeasy0823]

Hello,

I am new to Purplemath, and am experiencing some difficulty with the above subject. Here is the problem:

(Square root y + Square root y+7=7), I raised the entire equation to the power of 2, to elimnate the square root.
This is what I have so far:

y+y+7=49
Subtracted 7 from both sides
Gave me 2y=42
Divided 2 from both sides
Gave me y=21

But when plugged 21 in for y, didn't equal 7.

[little_dragon]

(Square root y + Square root y+7=7), I raised the entire equation to the power of 2, to elimnate the square root.
This is what I have so far: y+y+7=49

if U sqr both sides U still have roots:
(sqrt[y] + sqrt[y+7])^2 = 7^2
y + 2sqrt[y[sqrt[y+7] + y+7 = 49
do the sqring rite & it should come out rite:
2sqrt[7]sqrt[y+7]=49-7-2y
2sqrt[7]sqrt[y+7]=42-2y
sqrt[7]sqrt[y+7]=21-y
7[y+7]=(21-y)^2
keep going til U get the ans!