Resolved the doubt… Thanks for the help

You forgot class vi algebra. (a+b)^2

14,14%=(0.3*0.2)^2+(0.7*0.12)^2+ 2*0.3*0.2*0.7*0.12*correlation

To the right of the equal sign you have a formula for the * variance* of returns for the portfolio; to the left you have the

*standard deviation*of the portfolio’s returns.

Ooops…you are right.

you are missing the 2 in the formula is must be (.3^2*.2^2+.7^2*.12^2+2*.7*.3*.2*.12*1)^.5

In the special case where correlation = 1, the standard deviation of the portfolio will be the weighted average of the individual assets’ standard deviations.

In this case, 0.3(0.20) + 0,7(0.12) = 14.4%, so the correlation is therefore 1