Answer:
A
Step-by-step explanation:
Using the rule of exponents
[tex]a^{m}[/tex] × [tex]a^{n}[/tex] ⇔ [tex]a^{m+n}[/tex], thus
Given
[tex]x^{m}[/tex] × [tex]x^{4}[/tex] = [tex]x^{8}[/tex], that is
[tex]x^{4+m}[/tex] = [tex]x^{8}[/tex]
Since the bases are the same equate the exponents
4 + m = 8 ( subtract 4 from both sides )
m = 4 → A