ANSWER
The dot product is 10.
EXPLANATION
The given vectors are (2,4) and (1,2).
If we have the vectors
u=(a,b) and v=(c,d)
Then the dot product of the two vectors is given by
[tex]u \bullet \: v = ac + bd[/tex]
This implies that,
[tex](2,4) \bullet(1,2) = 2 \times 1 + 4 \times 2[/tex]
This simplifies to;
[tex](2,4) \bullet(1,2) = 2 + 8 = 10[/tex]