The fourth power of x plus 4 factoring? How to do? Gods help

The fourth power of x plus 4 factoring? How to do? Gods help

X^4+4 =X^4+4x^2-4X^2+4 =（X^4+4x^2+4）-4X^2 =(X^2+2)^2-4X^2 =(X^2+2-2X)(X^2+2+2X)

The decomposition of factor (1) (M + n) to the third power + 2m (M + n) + m (M + n) is a process,

(m+n)^3+2m（m+n）^2+m^2（m+n） =(m+n)[(m+n)^2+2m+m^2] =(m+n)[(m+n)+m]^2 =(m+n)(2m+n)^2

It is known that the fourth power of X + the third power of MX + nx-16 has the factors X-1 and X-2. Find the values of M and N, and decompose this polynomial. The great gods help us
Such as the title

Let X4 + MX3 + nx-16 = (x-1) (X-2) (x2 + ax + b) = (x2-3x + 2) (x2 + ax + b) get 2B = - 16 B-3A + 2 = 0 B = - 8 A = - 2 (x-1) (X-2) (x2-2x-8) = (x-1) (X-2) (x-4) (x + 2) = x4-5x3 + 20x-16 M = - 5 N = 20