You can put this solution on YOUR website!
The idea of solving equations is often a matter of "undoing" what has been done to the x, and usually in reverse order. Notice that in this equation, the x has a 4 added to it, the result is squared, and it equals 21. You need to UNDO those operations in reverse order. First undo the square, by square rooting both sides. Don't forget to put the PLUS or MINUS when you do this.
Next, undo the +4 by subtracting 4 from each side:
R^2 at SCC