Question

A (m,3), B (-1,7) e D=5

Answer 1

$5= \sqrt{(-1-m)^2+(7-3)^2} \\ \\ 5^2=( \sqrt{(-1-m)^2+(4)^2})^2 \\ \\ 25=(-1-m)^2+16 \\ \\ 25=(-1-m)(-1-m)+16 \\ \\ 1+m+m+m^2+16-25=0 \\ \\ m^2+2m-8=0 \\ \\ m_1=4 \\ m_2=-2$