Question 252435
Given, m + n =3 and m^2 + n^2 = 6
       (m+n)^2 = m^2+n^2+2m*n
        3^2    = 6+2m*n
            9  = 6+2m*n 
            3  = 2m*n
            m*n = 3/2
            m*n = 1.5
Next, m^3+n^3   = (m+n)*(m^2+n^2-m*n)
                = 3*(6-1.5)
                = 3*(4.5)
                =13.5