if the exppansion of (1+x)^m(1-x)^n ,the coefficients of x and x^2 are 3 and -6 respectively then find the value of m and n?

(1+x)^m(1-X)ⁿ

=(1+^mC₁X + ^mC₂X²+....^mC_mX^m) (1-ⁿC₁X+ⁿC₂X²-....+ⁿC_nXⁿ)

For coefficient of  X  => (^mC₁ - ⁿC₁) =3

m-n=3

??For coefficient of X²  => (^mC₂ + ⁿC₂ - ^mC_1.ⁿC₁)=-6

m(m-1)/2 + n(n-1)/2 -mn=-6

By solving these two eqⁿs we get

n=9  m=12