how do I solve a linear system equation with the two equations being y=-x+4 and x+y=4 by using substitution method

Question

how do I solve a linear system equation with the two equations being y=-x+4 and x+y=4  by using substitution method

shoba · Answer

y = -x + 4----1
x+y = 4----2

x + (-x+4)=4
is the equation correct?

aum · Answer

If you rearrange the given equations a little bit you will notice they are one and the same equation y = -x + 4.  So the two equations are dependent and therefore ANY point on the line y = -x + 4 is a solution and there are INFINITE number of solutions.

aum · Answer

If you follow the substitution method in shoba's reply where you take y from the first equation and put it in the second equation, you get: x - x + 4 = 4
or 4 = 4 which is ALWAYS true no matter what x is.  Therefore any value of x is a solution.  You just put that x  value in y = -x +4 and find the corresponding y value.  Thus there are infinite number of  solutions.