# Exercise Solution 3.14

This is a bit of a trick question. Its purpose is to emphasize to you the general applicability of formula [3.28]. To solve the problem, recognize that *Z* = *A* + *B*. You know the standard deviations and correlation of *A* and *B*, so you can directly apply [3.28] to obtain a standard deviation for *Z*. The result is 4.74. The information that *B* = *A*^{2} – 2*A* – 4 is extraneous.