ANSWER
The coordinates of the image are (2,2)
Step-by-step explanation
The mapping for a reflection across the line y=k is :
![(x,y)\to (x,2k-y)](https://img.qammunity.org/2020/formulas/mathematics/high-school/4rf9d74xxz348hutwi085kfozczpqzgsha.png)
We want to find the image of the point (2,-4) after a reflection in the line y=-1.
In this case k=-1.
![(2, - 4)\to (2,2( - 1)- - 4)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4eet53g5qnx231qn8yz9i41cwdekm5fnkl.png)
This simplifies to,
![(2, - 4)\to (2, - 2 + 4)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/gdzhtopymqj8lusd0oedzz0btvn9n9b29z.png)
![(2, - 4)\to (2, 2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/pphakksimus0gz5497t7jrnp1gi3l3b2u3.png)
Hence the image is (2,2)