Question 24637
You have to know the following:
a^3-b^3 = (a-b)(a^+ab+b^2)
Your Problem fits this pattern after factoring
out a "2" to get:
 2(125-8x^3) = 2 (5^3-(2x)^3)
= 2 (5-2x)(5^2+(5)(2x)+(2x)^2)
= 2 (5-2x)(25+10x+4x^2)

Cheers,
stan H.