Question

a^2+a-3 subtracted from 3a^2-5

Answer 1

3a^2 - 5 - (a^2 + a - 3) =
3a^2 - 5 - a^2 - a + 3 =
2a^2 - a - 2 

Answer 2

This sort of problem is one that initially appears complex but is actually quite simple, once you get the hang of it.  You just need to subtract each individual term in the first polynomial from the second polynomial.

First, I'll rewrite the second one so that it's easier to work with:

$3a^{2}+0a-5$

I added the a-term as a helpful placeholder — notice that no matter the value we choose for a, it will not change from the unmodified equation (because 0 times any number equals 0).  

So, 3a^2-a^2=2a^2 (that's the first term of our new polynomial)

0a-a=-a (the second term)

-5-(-3)=-2 (whenever you see two negative signs next to each other, you can replace them with a + sign.  So the problem simplifies to -5+3, or -2.  

The answer is 2a^2-a-2.