dzak said:
I do not understand the steps in solving this system equation by substitution:
x + 3y = 2..................................(1)
-x + y = 1..................................(2)
I'll do a similar but differen problem
2x + 3y = 8..................................(1)
-x + y = 1..................................(2)
Substitution involves writing "one variable" as a function of the "other".
If you work with the second equation - you can write:
y = 1 + x .................................(3)
Now
substitute 'y' in equation '2' by the expression you found in (3)
so we get
2x + 3
(1+x) = 8
2x + 3 + 3x = 8
5x + 3 = 8
5x = 5
x = 1..............................................(4)
now apply this value of 'x' into equation (3) to solve for 'y'
y = x + 1
y = 2.............................................(5)
Now put these values back into your original equation and check for correctness.
2x + 3y = 8
2*1 + 3*2 = 8
2 + 6 = 8
8 = 8...........................................checks
-x + y = 1
-1 + 2 = 1
1 = 1..........................................checks
So the calculated answers are correct.
