Question

Factor x^7 + 20x^5 + 100x^3 completely

Answer 1

take out x^3, so it would be x^3(x^4+20x^2+100)
now, let x^2 = a
then you have a^3/2( a^2+20a+100) = a^3/2( a+10)^2
substituting a = x^2,
x^3(x^2+10)^2