I not sure if you mean the gradient of the line or the equation, so here is both.
Gradient (=m) :
( 4, 4 ) ( 6, 5 )
( x1 , y1) ( x2, y2 )
m = y2-y1 / x2-x1
= -5-4 / 6 - 4
= -9 / 2 (as a fraction)
= -4.5 (as a decimal)
Equation of the line :
m = -9/2
( 4, 4 )
( a, b )
y - b =m (x - a)
y - 4= -9/2 (x - 4)
(Multiply both sides by 2 to get rid of fraction)
2y - 4 = -9 (x - 4)
2y - 4 = -9x + 36
2y = -9x + 36 + 4
2y = -9x + 40
2y + 9x = 40
Please feel free to ask if you have any questions
