If x+y+z=13 what is the value of (x-1)+(y+1)+(z-1)

12

Step-by-step explanation:

(x-1)+(y+1)+(z-1)

= x -1 + y + 1 + z - 1

= x + y + z -1

= (x + y + z) -1

given that x+y+z = 13, substitute this value into the equation aove

(x + y + z) -1

= 13 - 1

= 12

the function makes a strait line horizontally with no x intercept but a y intercept at 9.

check above link.

graphically?   well, you graph them both, the solutions is where they both intersect each other, since there are two solutions, meaning they will meet twice, or namely the linear will run into the quadratic curve twice, and where they meet, those x,y coordinates are the solutions to the system.