How do I use the solve command

I am trying to solve for a certain M that will satisfy 2 equations using the solve command. I know my final answer is supposed to be 1.2, and I have defined my equations. I am not sure if I am incorrectly using the solve command or have incorrectly defined the equations.

r   = 1.4;
rm1 = r-1;
rp1 = r+1;

syms M
A_AS=sqrt((1/M^2)*(((2+rm1*M^2)/rp1)^(rp1/rm1)));
Po2_Po1=((rm1*.5*M^2)/(1+rm1*.5*M^2))^(r/rm1)*(1/(((2*r)/rp1)*M^2-(rm1/rp1)))^(1/rm1);
Ac_At = A_AS*Po2_Po1 == 1.2;
M = solve(Ac_At,M)

I would appreciate the help, thank you for your time

[Walter Roberson]

MATLAB is finding one of the roots but not all of the roots.

For that those equations, are two real roots:

temp = roots([3630287, 15558480, -12224520, 3598560, -521640, 37584, -1080]);
temp(imag(temp)~=0) = [];
temp(temp<0) = [];
sol = sqrt(temp);

along with the negative of that. Approximately +/- 0.386916692037127

We do not know if your equations are right...

[Jose Camorlinga Medina]

Thank you for your help.