1. Looks right!

2.

√(x+3)=2 √x

√(x+3)²=2² √x²

x+3 = 4x [Note: the square root and square cancel each other out, just leaving (x+3)]

Now, subtract 4x from both sides: x+3 - 4x = 4x - 4x

Simplify: -3x + 3 = 0

So, x must be 1

(Or, you could be formal, and follow the steps:

Subtract 3 from both sides: -3x = -3

divide by -3: x = 1)