3:
a: 5m^3-45m
=5m(m^2-9)
=5m(m-3)(m+3)
b: x^4-16y^4
=(x^2-4y^2)(x^2+4y^2)
=(x^2+4y^2)(x-2y)*(x+2y)
c: -x^2y+xy^2+1/4x^3
=x(1/4x^2-xy+y^2)
=x(1/2x-y)^2
d: x^2+6x-t^2+9
=(x^2+6x+9)-t^2
=(x+3)^2-t^2
=(x+3+t)(x+3-t)
e: a^2-ab+a-b
=a(a-b)+(a-b)
=(a-b)(a+1)
g: x^3-2x^2-x+2
=x^2(x-2)-(x-2)
=(x-2)(x^2-1)
=(x-2)(x+1)(x-1)