Question 366111
{{{10x^8-15x^4+20x^12 = 5x^4*(2x^4-3 + 4x^8)= 5x^4*(4x^8 + 2x^4-3)}}}.  Now there are two polynomial factors  {{{5x^4}}} and {{{4x^8 + 2x^4-3}}}.   {{{4x^8 + 2x^4-3}}} cannot be factored into polynomials of lower degree having rational coefficients, and thus, having the higher degree, is the GCF of the given polynomial.