complete the squaer to get into form
(x-h)²+(y-k)²=r²
where the center is (h,k) and the radius is r
so
group x and y terms together
(x²+4x)+(y²-10y)=7
take 1/2 of each coefient and square it
4/2=2, 2²=4
-10/2=-5, (-5)²=25
add 4+25 to both sides
(x²+4x)+(y²-10y)+4+25=7+4+25
(x²+4x+4)+(y²-10y+25)=36
factor perfect squares
(x+2)²+(y-5)²=36
convert to the form
(x-(-2))²+(y-5)²=6²
center is (-2,5) and radius is 6