9(x+8)8(x-9)8+(x+8)9×(x-9)7.
We look for the lowest power of x+8, which is 8th power so this is a common factor.
Now look for the lowest power of x-9, which is 7th power. Therefore (x+8)8(x-9)7 is the common factor.
Factorisation is: (x+8)8(x-9)7(9(x-9)+1)=(x+8)8(x-9)7(9x-81+1)=(x+8)8(x-9)7(9x-80).