ANSWER
The coefficient is 70.
EXPLANATION
The given binomial expression is
[tex](x+y)^8 [/tex]
The specific term of a binomial expansion can be determined using the formula,
[tex]T_{r+1}= nC_ra^{n-r}b^r[/tex]
where
[tex]n=8,r=4,a=x,b=y[/tex]
We substitute these values into the formula to get,
[tex]T_{4+1}= 8C_4x^{8-4}y^4[/tex]
We simplify to get,
[tex]T_{5}= 70x^{4}y^4[/tex]
Hence the coefficient is 70.