新gre数学重要考点：Subtracting Monomials
Subtracting Monomials
To subtract a monomial from another of the same variables just subtract the coefficients. Only two like monomials can be subtracted from each other.
Example:
By subtracting 3x from 4x, we get (4-3)x=x.
By subtracting 3xy from 2xy, we get (2-3)xy=-xy.
By subtracting bx from ax, we get ax-bx=(a-b)x.
Remember:
Monomials can be subtracted only if they have the same variables with identical powers.
