factorise

Question

a) m^3-27n^3
b) 64a^3b^4+216a^6b
c) (a+b)-a-b

Answer 1

1.
from A^3 - B^3 = (A-B)(A^2 + AB + B^2)
m^3 - 27n^3
= (m-3n)(m^2 + 3mn + 9n^2)

2.
64a^3b^4+216a^6b
= 8a^3b(8b^3 + 27a^3)
= 8a^3 b(2b+3a)(4b^2 - 6ab + 9a^2)

3. (a+b) - a - b
= a+b-a-b
= 0