Respuesta :

Find the slope m.

m = (-1 -(-1))/(15 - 7)

m = (-1 + 1)/8

m = 0/8

m = 0

Now use the point-slope formula.

y - y_1 = m(x - x_1)

y - (-1) = (0)(x - 7)

y + 1 = 0

y = - 1

Done!