Does (4,5) represent a solution to the equation x+y+z=9?

Yes

Step-by-step explanation:

you substitute 4 for x and 5 for y.  

4 + 5 + z = 9

z = 0

so when you plug all of it together it equals 9.

1) no, because a solution must be an ordered triple pair (x,y,z)

2) { x+y+z=5    

   { 2x-3y+z=7      

   { x+2y-4z=2

3) infinity many solutions

4) use equations (1) and (2) to eliminate y

5) solve one equation for one of its varaibles  

Step-by-step explanation:

should be 100% on the quick check if you put those answers

1^3 + 2^3 + 3^3 +4^3 = (1+2+3+4)^2

step-by-step explanation:

i am only able to answer the first part. i am not sure about the second part. sorry