Constraint given region

2x+3y-5=0，

x≥0，

y≥0，

In this regard, I learned after painting,

All points (x, y) in this region are in the region of x+y+ 1 > 0.

That is x+y+ 1 > 0.

∴z=x+y+ 1

y=-x+(z- 1)

It can be seen that the greater the longitudinal intercept of the objective function, the greater the z- 1 and the greater the z.

k=- 1，k