How do you check your solutions to a systems of equations using the substitution method?

1 Answer
Jan 26, 2015

I created a video with a more detail explanation here.

To check a system of equations by substitution, you plug your values for x and y into the original equations. If both simplified expressions are true then your answer is correct.

For example: To check if (2, -3) was the correct solution for the system of equation: y = -2x + 1 and y = x - 5,
substitute 2 for x and -3 for y into each equation

y = -2x + 1
-3 = -2(2) + 1
-3 = -4 + 1
-3 = -3

and

y = x - 5
-3 = 2 - 5
-3 = -3

Since x = 2 and y = -3 worked for both equations I know that (2, -3) is the solution to this system of equations.