If (sqrt{x^2 + 9}) = x + 1, solve for x

A.
5 
B.
4 
C.
3 
D.
2 
E.
1
Correct Answer: Option B
Explanation
(sqrt{x^2 + 9}) = x + 1
x^{2} + 9 = (x + 1)^{2} + 1
0 = x^{2} + 2x + 1 – x^{2} – 9
= 2x – 8 = 0
2(x – 4) = 0
x = 4
(sqrt{x^2 + 9}) = x + 1
x^{2} + 9 = (x + 1)^{2} + 1
0 = x^{2} + 2x + 1 – x^{2} – 9
= 2x – 8 = 0
2(x – 4) = 0
x = 4