Explanation:
(-3x⁴)(-4x²)
as multiplication is commutative (that means the sequence of the factors is irrelevant), we get
-3×-4×x⁴×x²
we can combine everything of the same type (constants or variable names).
-3×-4 = 12
remember, -×- = +
x⁴×x² = x⁶
remember, when multiplying terms with the same base variable, we can simply add the exponents.
why ? because an exponent is a short way of saying that the base variable has to be multiplied by itself that many times.
e.g.
a³ = a×a×a
a⁷ = a×a×a×a×a×a×a
a³×a⁷ = a×a×a × a×a×a×a×a×a×a = a¹⁰
that's why.
so, the complete simplified expression is
12x⁶