The reflection across the x-axis is made by changing the sign of the y coordinate and maintaining the x coordinate, that is:
[tex](x,y)\to(x,-y)[/tex]
So, we can just apply this transformation to each vertex of the original triangle:
[tex]\begin{gathered} C=(-3,-4)\to C^{\prime}=(-3,-(-4))=(-3,4) \\ M=(-3,6)\to M^{\prime}=(-3,-6) \\ S=(-6,5)\to S^{\prime}=(-6,-5) \end{gathered}[/tex]
So, the coordinates of the image triangle are:
[tex]\begin{gathered} C^{\prime}=(-3,4) \\ M^{\prime}=(-3,-6) \\ S^{\prime}=(-6,-5) \end{gathered}[/tex]
