Question 359098
(3a4-2a2+5a-10)-(2a4+4a2+5a-2)

remove first set of parentheses:
{{{3a^4 - 2a^2 + 5a - 10 -(2a^4 + 4a^2 + 5a - 2)}}}

apply "-" sign to second parentheses (distributive prop):
{{{3a^4 - 2a^2 + 5a - 10 - 2a^4 - 4a^2 - 5a -(-2)}}}

the - of a - becomes a + :
{{{3a^4 - 2a^2 + 5a - 10 - 2a^4 - 4a^2 - 5a + 2}}}

combine like terms:
{{{3a^4 - 2a^4 - 2a^2 -4a^2 + 5a - 5a - 10 + 2}}}

Factor out the variables that are alike:
{{{(3-2)a^4 + (-2-4)a^2 + (5-5)a + (-10 + 2)}}}
{(1)a^4 + (-6)a^2 + 0a + (-8)}}}

0a is just 0, makea the "a" term go away:
{{{a^4 -6a^2 -8}}}

can try to factor as squares, but it doesn't work out:
8 = (-4) x (+2) product factors cannot add to make 6.