Factoriser:
H=x^2-9= (x-3)(x+3)
I= 4x^2-16= (2x)²-4²= (2x-4)(2x+4)= 2*2(x-2)(x+2)= 4(x-2)(x+2).
J=16x^2-25=(4x)²-5²= (4x-5)(4x+5)
K=81t^2-49= (9t)²-7²= (9t-7)(9t+7)
L=144m^2-36= 36(4m²-1)= 36((2m)²- 1²)= 36(2m-1)(2m+1)
N=1-x^1= 1-x
O=(x+7)^2-(x-3)^2= (x+7-x + 3)(x+7+x-3)= 10(2x+4)= 20(x+2).