How would i write this in function notation?

To write this in function notation, first find the coordinates of the 2 points given.

Assuming each line segment below the y axis decreases by 1

Assuming the lines past the X axis to the right increase by 1

Point A - (0,-5)
Point B - (5,0)

Find the slope using the equation for slope.

M = y2 - y1/ x2 - x1
M = 0 - -5/ 5 - 0
M = 0+5/5
M = 5/5 = 1 - slope is 1.

Now put the information you know.

Slope and y intercept in slope y intercept equation

Y = mx + b
Y = 1x + - 5
Y = X - 5.

In function notation the equation is y = X - 5.