ANSWER
The coefficient is 70.
Step-by-step explanation
The given binomial expression is
![(x+y)^8](https://img.qammunity.org/2020/formulas/mathematics/middle-school/hhxz7z7cnu5bj7lq2cvcptqsob8t3g0zfh.png)
The specific term of a binomial expansion can be determined using the formula,
![T_(r+1)= nC_ra^(n-r)b^r](https://img.qammunity.org/2020/formulas/mathematics/middle-school/xcgwvb5i3bjs1oq7dbbk4g242ck0qkjdxf.png)
where
![n=8,r=4,a=x,b=y](https://img.qammunity.org/2020/formulas/mathematics/middle-school/yhdqf1dtp3ro4fmmturpwvlzchc486j19b.png)
We substitute these values into the formula to get,
![T_(4+1)= 8C_4x^(8-4)y^4](https://img.qammunity.org/2020/formulas/mathematics/middle-school/xuq7n1ab84cqfel3u1x8lc4s6eukflnkcr.png)
We simplify to get,
![T_(5)= 70x^(4)y^4](https://img.qammunity.org/2020/formulas/mathematics/middle-school/e3707gsv3cvwhq11agl0z9aqlvtkzon8zr.png)
Hence the coefficient is 70.