We have a line that passes through the point P:
P = (2, -1)
And that has a slope m = 5. Using the point-slope form of the linear equation:
(y - y0) = m*(x - x0) ...(1)
Where x0 and y0 are the coordinates of any point contained in the line. In particular, if the point is P:
x0 = 2
y0 = -1
Then, replacing these values on (1):
(y - (-1) = 5*(x - 2)
y + 1 = 5x - 10
Finally:
y = 5x - 11